Vibrating device and image equipment having the same

ABSTRACT

A vibrating device includes first and second members, each shaped almost like a rectangle and composed of first and second parts, a connection member composed of a first circuit which inputs an electrical signal to the first part, a second circuit which outputs an electrical signal generated in the second part, and a connection part which connects the first and second circuits electrically, and a drive unit which drives the first and second members while the first and second circuits remain connected by the connection part. The first and second members are shaped symmetrically to one another in weight balance with respect to a virtual symmetry axis at the same distance from the first and second members and also to an virtual centerline connecting gravity centers of the first and second members. The second member is shaped asymmetrically in vibrational amplitude with respect to its vibrational axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Applications No. 2009-142635, filed Jun. 15, 2009;and No. 2009-261154, filed Nov. 16, 2009, the entire contents of both ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to image equipment having image formingelements such as an image sensor element or a display element, and alsoto a vibrating device designed to vibrate the dust-screening member thatis arranged at the front of each image forming element of such an imageequipment.

2. Description of the Related Art

As image equipment having image forming elements, there is known animage acquisition apparatus that has an image sensor element configuredto produce a video signal corresponding to the light applied to itsphotoelectric conversion surface. Also known is an image projector thathas a display element, such as liquid crystal element, which displays animage on a screen. In recent years, image equipment having such imageforming elements have been remarkably improved in terms of imagequality. If dust adheres surface of the image forming element such asthe image sensor element or display element or to the surface of thetransparent member (optical element) that is positioned in front of theimage forming element, the image produced will have shadows of the dustparticles. This makes a great problem.

For example, digital cameras of called “lens-exchangeable type” havebeen put to practical use, each comprising a camera body and aphotographic optical system removably attached to the camera body. Thelens-exchangeable digital camera is so designed that the user can usevarious kinds of photographic optical systems, by removing thephotographic optical system from the camera body and then attaching anyother desirable photographic optical system to the camera body. When thephotographic optical system is removed from the camera body, the dustfloating in the environment of the camera flows into the camera body,possibly adhering to the surface of the image sensor element or to thesurface of the transparent member (optical element), such as a lens,cover glass or the like, that is positioned in front of the image sensorelement. The camera body contains various mechanisms, such as a shutterand a diaphragm mechanism. As these mechanisms operate, they producedust, which may adhere to the surface of the image sensor element aswell.

Projectors have been put to practical use, too, each configured toenlarge an image displayed by a display element (e.g., CRT or liquidcrystal element) and project the image onto a screen so that theenlarged image may be viewed. In such a projector, too, dust may adhereto the surface of the display element or to the surface of thetransparent member (optical element), such as a lens, cover glass or thelike, that is positioned in front of the display element, and enlargedshadows of the dust particles may inevitably be projected to the screen.

Various types of mechanisms that remove dust from the surface of theimage forming element or the transparent member (optical element) thatis positioned in front of the image sensor element, provided in suchimage equipment have been developed.

In an electronic image acquisition apparatus disclosed in, for example.US 2004/0169761 A1, a ring-shaped piezoelectric element (vibratingmember) is secured to the circumferential edge of a glass plat shapedlike a disc (dust-screening member). When a voltage of a prescribedfrequency is applied to the piezoelectric element, the glass plat shapedlike a disc undergoes a standing-wave, bending vibration having nodes atthe concentric circles around the center of the glass plat shaped like adisc. This vibration removes the dust from the glass disc. The vibrationproduced by the voltage of the prescribed frequency is a standing wavehaving nodes at the concentric circles around the center of the disc.The dust-screening member is held by dust-screening member holdingmembers that contact the dust-screening member at the nodes of standingwaves that form concentric circles. The dust-screening member holdingmembers maintain dust screening condition between the dust-screeningmember and the image sensor element.

Jpn. Pat. Appln. KOKAI Publication No. 2007-267189 discloses arectangular dust-screening member and piezoelectric elements secured tothe opposite sides of the dust-screening member, respectively. Thepiezoelectric elements produce vibration at a predetermined frequency,resonating the dust-screening member. Vibration is thereby achieved insuch mode that nodes extend parallel to the sides of the dust-screeningmember. In order to remove dust from the nodes of vibration, thedust-screening member is resonated at different frequencies,accomplishing a plurality of standing-wave vibrational modes, therebychanging the positions of nodes. Any one of the vibrational modesachieves bending vibration having nodes extending parallel to the sidesof the dust-screening member.

Further, Jpn. Pat. Appln. KOKAI Publication No. 2009-38741 discloses aconfiguration in which vibrating plates (piezoelectric elements) areprovided at the opposite sides of a low-pass filter (dust-screeningmember) that is shaped like a rectangular plate. The vibrating plateprovided at one side is vibrated. The voltage generated as the vibratingplate provided at the other side is detected. From the voltage detected,it is determined whether the vibration application function is a normalone or not. If the vibration application function is a normal one, bothvibrating plates are vibrated to remove dust from the low-pass filter.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda vibrating device comprising:

a dust-screening member shaped like a plate as a whole, having front andback surfaces and having a light-transmitting region for transmittinglight between the front surface and the back surface;

a support member configured to support the dust-screening member,thereby to render the back surface of the dust-screening memberairtight;

a first vibrating member shaped almost like a rectangle, arranged at afirst outer circumferential part of the dust-screening member andcomposed of a first vibration application part configured to expand andcontract when supplied with an electrical signal for expanding andcontracting and a first non-vibration application part configured not tosupplied with the electrical signal for expanding and contracting;

a second vibrating member shaped almost like a rectangle, arranged at asecond outer circumferential part of the dust-screening member, whichopposes the first outer circumferential part of the dust-screeningmember, and composed of a second vibration application part configuredto expand and contract when supplied with the electrical signal forexpanding and contracting and a second non-vibration application partconfigured not to supplied with the electrical signal for expanding andcontracting;

a connection member composed of a first circuit, a second circuit and aconnection part, the first circuit configured to input an electricalsignal to the first vibration application part, the second circuitconfigured to output, from the second vibration application part, anelectrical signal generated in the second vibration application partbased on a vibration of the first vibration application part when anelectrical signal is input to the first circuit, and the connection partconfigured to connect the first and second circuits electrically; and

a drive unit configured to drive the first and second vibrating memberswhile the first and second circuits remain connected by the connectionpart,

wherein the first and second vibrating members are shaped symmetricallyto one another in weight balance with respect to a virtual symmetry axisat the same distance from the first and second vibrating members andalso to an virtual centerline connecting gravity centers of the firstand second vibrating members, and

the second vibrating member which receives the vibration has avibrational axis and is shaped asymmetrically in vibrational amplitudewith respect to the vibrational axis.

According to a second aspect of the present invention, there is providedan image equipment comprising:

an image forming element having an image surface on which an opticalimage is formed;

a dust-screening member shaped like a plate as a whole, having front andback surfaces and having a light-transmitting region for transmittinglight between the front surface and the back surface;

a support member configured to support the dust-screening member, tospace the light-transmitting region of the dust-screening member, apartfrom the image surface of the image forming element by a predetermineddistance, and to render the back surface of the dust-screening memberairtight;

a first vibrating member shaped almost like a rectangle, arranged at afirst outer circumferential part of the dust-screening member andcomposed of a first vibration application part configured to expand andcontract when supplied with an electrical signal for expanding andcontracting and a first non-vibration application part configured not tosupplied with the electrical signal for expanding and contracting;

a second vibrating member shaped almost like a rectangle, arranged at asecond outer circumferential part of the dust-screening member, whichopposes the first outer circumferential part of the dust-screeningmember, and composed of a second vibration application part configuredto expand and contract when supplied with the electrical signal forexpanding and contracting and a second non-vibration application partconfigured not to supplied with the electrical signal for expanding andcontracting;

a connection member composed of a first circuit, a second circuit and aconnection part, the first circuit configured to input an electricalsignal to the first vibration application part, the second circuitconfigured to output, from the second vibration application part, anelectrical signal generated in the second vibration application partbased on a vibration of the first vibration application part when anelectrical signal is input to the first circuit, and the connection partconfigured to connect the first and second circuits electrically; and

a drive unit configured to drive the first and second vibrating memberswhile the first and second circuits remain connected by the connectionpart,

wherein the first and second vibrating members are shaped symmetricallyto one another in weight balance with respect to a virtual symmetry axisat the same distance from the first and second vibrating members andalso to an virtual centerline connecting gravity centers of the firstand second vibrating members, and

the second vibrating member which receives the vibration has avibrational axis and is shaped asymmetrically in vibrational amplitudewith respect to the vibrational axis.

Advantages of the invention will be set forth in the description whichfollows, and in part will be obvious from the description, or may belearned by practice of the invention. Advantages of the invention may berealized and obtained by means of the instrumentalities and combinationsparticularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a block diagram schematically showing an exemplary systemconfiguration, mainly electrical, of a lens-exchangeable, single-lensreflex electronic camera (digital camera) that is a first embodiment ofthe image equipment according to this invention;

FIG. 2A is a vertical side view of an image sensor element unit of thedigital camera, which includes a dust removal mechanism (or a sectionalview taken along line A-A shown in FIG. 2B);

FIG. 2B is a front view of the dust removal mechanism, as viewed fromthe lens side;

FIG. 3 is an exploded perspective view showing a major component(vibrator) of the dust removal mechanism;

FIG. 4 is a front view showing the structure of the flexible printedboard connected to the piezoelectric elements of the vibrator;

FIG. 5A is a front view of a dust filter, explaining how the dust filteris vibrated;

FIG. 5B is a sectional view of the dust filter, taken along line B-Bshown in FIG. 5A;

FIG. 5C is a sectional view of the dust filter, taken along line C-Cshown in FIG. 5A;

FIG. 5D is a sectional view of the dust filter, taken along line D-Dshown in FIG. 5A;

FIG. 6 is a diagram explaining the length of the long sides and that ofthe short sides of the dust filter;

FIG. 7A is a diagram explaining the concept of vibrating the dustfilter;

FIG. 7B is a front view of the dust filter vibrated in such a mode thatnode areas, where vibration hardly occurs, form a lattice pattern;

FIG. 8 is a diagram explaining how the dust filter is vibrated inanother mode;

FIG. 9 is a diagram explaining how the dust filter is vibrated in stillanother mode;

FIG. 10 is a diagram showing the relation between the aspect ratio ofthe dust filter shown in FIG. 5A and the vibration speed ratio of thecenter part of the dust filter;

FIG. 11 is a diagram showing the relation that the voltage detected bysuch a vibration detector as shown in FIG. 12 has with the vibrationspeed ratio of the dust filter that vibrates in the vibrational mode ofFIG. 9 when the dust filter control circuit applies a signal voltage tothe two piezoelectric elements;

FIG. 12 is a diagram illustrating the concept of a vibration detector;

FIG. 13 is a diagram showing another configuration the dust filter and aflexible printed board may have;

FIG. 14 is a diagram showing still another configuration the dust filterand the flexible printed board may have;

FIG. 15 is a conceptual diagram of the dust filter, explaining thestanding wave that is produced in the dust filter;

FIG. 16A is a diagram showing an electric equivalent circuit that drivesthe vibrator at a frequency near the resonance frequency;

FIG. 16B is a diagram showing an electric equivalent circuit that drivesthe vibrator at the resonance frequency;

FIG. 17 is a circuit diagram schematically showing the configuration ofa dust filter control circuit;

FIG. 18 is a timing chart showing the signals output from the componentsof the dust filter control circuit;

FIG. 19A is the first part of a flowchart showing an exemplary camerasequence (main routine) performed by the microcomputer for controllingthe digital camera body according to the first embodiment;

FIG. 19B is the second part of the flowchart showing the exemplarycamera sequence (main routine);

FIG. 20 is a flowchart showing the operating sequence of “silentvibration” that is a subroutine shown in FIG. 19A;

FIG. 21 is a flowchart showing the operation sequence of the “displayprocess” performed at the same time Step S201 of “silent vibration,”i.e. subroutine (FIG. 20), is performed;

FIG. 22 is a flowchart showing the operating sequence of the “displayprocess” performed at the same time Step S203 of “silent vibration,”i.e., or subroutine (FIG. 20), is performed;

FIG. 23 is a flowchart showing the operating sequence of the “displayprocess” performed at the same time Step S205 of “silent vibration,”i.e., subroutine (FIG. 20), is performed;

FIG. 24 is a diagram showing the form of a resonance-frequency wavecontinuously supplied to vibrating members during silent vibration;

FIG. 25 is a flowchart showing the operating sequence of “silentvibration,” i.e., subroutine in the operating sequence of the digitalcamera that is a second embodiment of the image equipment according tothe present invention; and

FIG. 26 is a diagram showing the configuration of the vibration detectorused in a third embodiment of the image equipment according to thisinvention.

DETAILED DESCRIPTION OF THE INVENTION

Best modes of practicing this invention will be described with referenceto the accompanying drawings.

First Embodiment

An image equipment according to this invention, which will beexemplified below in detail, has a dust removal mechanism for the imagesensor element unit that performs photoelectric conversion to produce animage signal. Here, a technique of improving the dust removal functionof, for example, an electronic camera (hereinafter called “camera” willbe explained. The first embodiment will be described, particularly inconnection with a lens-exchangeable, single-lens reflex electroniccamera (digital camera), with reference to FIGS. 1 to 2B.

First, the system configuration of a digital camera 10 according to thisembodiment will be described with reference to FIG. 1. The digitalcamera 10 has a system configuration that comprises body unit 100 usedas camera body, and a lens unit 200 used as an exchange lens, i.e., oneof accessory devices.

The lens unit 200 can be attached to and detached from the body unit 100via a lens mount (not shown) provided on the front of the body unit 100.The control of the lens unit 200 is performed by the lens-controlmicrocomputer (hereinafter called “Lucom”) 201 provided in the lens unit200. The control of the body unit 100 is performed by the body-controlmicrocomputer (hereinafter called “Bucom” 101 provided in the body unit100. By a communication connector 102, the Lucom 210 and the Bucom 101are electrically connected to each other, communicating with each other,while the lens unit 200 remains attached to the body unit 100. The Lucom201 is configured to cooperate, as subordinate unit, with the Bucom 101.

The lens unit 200 further has a photographic lens 202, a diaphragm 203,a lens drive mechanism 204, and a diaphragm drive mechanism 205. Thephotographic lens 202 is driven by a DO motor (not shown) that isprovided in the lens drive mechanism 204. The diaphragm 203 is driven bya stepping motor (not shown) that is provided in the diaphragm drivemechanism 205. The Lucom 201 controls these motors in accordance withthe instructions made by the Bucom 101.

In the body unit 100, a penta-prism 103, a screen 104, a quick returnmirror 105, an ocular lens 106, a sub-mirror 107, a shutter 108, an AFsensor unit 109, an AF sensor drive circuit 110, a mirror drivemechanism 111, a shutter cocking mechanism 112, a shutter controlcircuit 113, a photometry sensor 114, and a photometry circuit 115 arearranged as shown in FIG. 1. The penta-prism 103, the screen 104, thequick return mirror 105, the ocular lens 106, and the sub-mirror 107 aresingle-lens reflex components that constitute an optical system. Theshutter 108 is a focal plane shutter arranged on the photographicoptical axis. The AF sensor unit 109 receives a light beam reflected bythe sub-mirror 107 and detects the degree of defocusing.

The AF sensor drive circuit 110 controls and drives the AF sensor unit109. The mirror drive mechanism 111 controls and drives the quick returnmirror 105. The shutter cocking mechanism 112 biases the spring (riotshown) that drives the front curtain and rear curtain of the shutter108. The shutter control circuit 113 controls the motions of the frontcurtain and rear curtain of the shutter 108. The photometry sensor 114detects the light beam coming from the penta-prism 103. The photometrycircuit 115 performs a photometry process on the basis of the light beamdetected by the photometry sensor 114.

In the body unit 100, an image acquisition unit 116 is further providedto perform photoelectric conversion on the image of an object, which haspassed through the above-mentioned optical system. The image acquisitionunit 116 is a unit composed of a CCD 117 that is an image sensor elementas an image forming element, an optical low-pass filter (LPF) 118 thatis arranged in front of the CCD 117, and a dust filter 119 that is adust-screening member. Thus, in this embodiment, a transparent glassplate (optical element) that has, at least at its transparent part, arefractive index different from that of air is used as the dust filter119. Nonetheless, the dust filter 119 is not limited to a glass plate(optical element). Any other member (optical element) that exists in theoptical path and can transmit light may be used instead. For example,the transparent glass plate (optical element) may be replaced by anoptical low-pass filter (LPF), an infrared-beam filter, a deflectionfilter, a half mirror, or the like. In this case, the frequency anddrive time pertaining to vibration and the position of a vibrationmember (later described) are set in accordance with the member (opticalelement). The CCD 117 is used as an image sensor element. Nonetheless,any other image sensor element, such as CMOS or the like, may be usedinstead.

As mentioned above, the dust filter 119 can be selected from variousdevices including an optical low-pass filter (LPF). However, thisembodiment will be described on the assumption that the dust filter is aglass plate (optical element).

To the circumferential edge of the dust filter 119, two piezoelectricelements 120 a and 120 b are attached, opposing each other across thecenter of the dust filter 119. The piezoelectric elements 120 a and 120b constitute a vibrating member and are almost rectangular. (The words“almost rectangular” mean a rectangular shape or a shape similarthereto.) The piezoelectric elements 120 a and 120 b have two electrodeseach. A dust filter control circuit 121, which is a drive unit, drivesthe piezoelectric elements 120 a and 120 b at the frequency determinedby the size and material of the dust filter 119. As the piezoelectricelements 120 a and 120 b vibrate, the dust filter 119 undergoes specificvibration. Dust can thereby be removed from the surface of the dustfilter 119. To the image acquisition unit 116, an anti-vibration unit isattached to compensate for the motion the hand holding the digitalcamera 10.

The digital camera 10 according to this embodiment further has a CCDinterface circuit 122, a liquid crystal monitor 123, an SDRAM 124, aFlash ROM 125, and an image process controller 126, thereby to performnot only an electronic image acquisition function, but also anelectronic record/display function. The CCD interface circuit 122 isconnected to the CCD 117. The SDRAM 124 and the Flash ROM 125 functionas storage areas. The image process controller 126 uses the SDRAM 124and the Flash ROM 125, to process image data. A recording medium 127 isremovably connected by a communication connector (not shown) to the bodyunit 100 and can therefore communicate with the body unit 100. Therecording medium 127 is an external recording medium, such as one ofvarious memory cards or an external HOD, and records the image dataacquired by photography. As another storage area, a nonvolatile memory128, e.g., EEPROM, is provided and can be accessed from the Bucom 101.The nonvolatile memory 128 stores prescribed control parameters that arenecessary for the camera control.

To the Bucom 101, there are connected an operation display LCD 129, anoperation display LED 130, a camera operation switch 131, and a flashcontrol circuit 132. The operation display LCD 129 and the operationdisplay LED 130 display the operation state of the digital camera 10,informing the user of this operation state. The operation display LED129 or the operation display LED 130 has, for example, a display unitconfigured to display the vibration state of the dust filter 119 as longas the dust filter control circuit 121 keeps operating. The cameraoperation switch 131 is a group of switches including, for example, arelease switch, a mode changing switch, a power switch, which arenecessary for the user to operate the digital camera 10. The flashcontrol circuit 132 drives a flash tube 133.

In the body unit 100, a battery 134 used as power supply and apower-supply circuit 135 are further provided. The power-supply circuit135 converts the voltage of the battery 134 to a voltage required ineach circuit unit of the digital camera 10 and supplies the convertedvoltage to the each circuit unit. In the body unit 100, too, a voltagedetecting circuit (not shown) is provided, which detects a voltagechange at the time when a current is supplied from an external powersupply though a jack (not shown).

The components of the digital camera 10 configured as described aboveoperate as will be explained below. The image process controller 126controls the CCD interface circuit 122 in accordance with theinstructions coming from the Bucom 101, whereby image data is acquiredfrom the CCD 117. The image data is converted to a video signal by theimage process controller 126. The image represented by the video signalis displayed by the liquid crystal monitor 123. Viewing the imagedisplayed on the liquid crystal monitor 123, the user can confirm theimage photographed.

The SDRAM 124 is a memory for temporarily store the image data and isused as a work area in the process of converting the image data. Theimage data is held in the recording medium 127, for example, after ithas been converted to JPEG data.

The mirror drive mechanism 111 is a mechanism that drives the quickreturn mirror 105 between an up position and a down position. While thequick return mirror 105 stays at the down position, the light beamcoming from the photographic lens 202 is split into two beams. One beamis guide to the AF sensor unit 109, and the other beam is guided to thepenta-prism 103. The output from the AF sensor provided in the AF sensorunit 109 is transmitted via the AF sensor drive circuit 110 to the Bucom101. The Bucom 101 performs the distance measuring of the known type. Inthe meantime, a part of the light beam, which has passed through thepenta-prism 103, is guided to the photometry sensor 114 that isconnected to the photometry circuit 115. The photometry circuit 115performs photometry of the known type, on the basis of the amount oflight detected by the photometry sensor 114.

The image acquisition unit 116 that includes the CCD 117 will bedescribed with reference to FIGS. 2A and 2B. Note that the hatched partsshown in FIG. 2B show the shapes of members clearly, not to illustratingthe sections thereof.

As described above, the image acquisition unit 116 has the CCD 117, theoptical LPF 118, the dust filter 119, and the piezoelectric elements 120a and 120 b. The CCD 117 is an image sensor element that produces animage signal that corresponds to the light applied to its photoelectricconversion surface through the photographic optical system. The opticalLPF 118 is arranged at the photoelectric conversion surface of the CCD117 and removes high-frequency components from the light beam comingfrom the object through the photographic optical system. The dust filter119 is a dust-screening member arranged in front of the optical LPF 118and facing the optical LPF 118, spaced apart therefrom by apredetermined distance. The piezoelectric elements 120 a and 120 b arearranged on the circumferential edge of the dust filter 119 and arevibrating members for applying specific vibration to the dust filter119.

The CCD chip 136 of the CCD 117 is mounted directly on a flexiblesubstrate 137 that is arranged on a fixed plate 138. From the ends ofthe flexible substrate 137, connection parts 139 a and 139 b extend.Connectors 140 a and 140 b are provided on a main circuit board 141. Theconnection parts 139 a and 139 b are connected to the connectors 140 aand 140 b, whereby the flexible substrate 137 is connected to the maincircuit board 141. The CCD 117 has a protection glass plate 142. Theprotection glass plate 142 is secured to the flexible substrate 137,with a spacer 143 interposed between it and the flexible substrate 137.

Between the CCD 117 and the optical LPF 118, a filter holding member 144made of elastic material is arranged on the front circumferential edgeof the CCD 117, at a position where it does not cover the effective areaof the photoelectric conversion surface of the CCD 117. The filterholding member 144 abuts on the optical LPF 118, at a part close to therear circumferential edge of the optical LPF 118. The filter holdingmember 144 functions as a sealing member that maintains the junctionbetween the CCD 117 and the optical LPF 118 almost airtight. A holder145 is provided, covering seals the CCD 117 and the optical LPF 118 inairtight fashion. The holder 145 has a rectangular opening 146 in a partthat is substantially central around the photographic optical axis. Theinner circumferential edge of the opening 146, which faces the dustfilter 119, has a stepped part 147 having an L-shaped cross section.Into the opening 146, the optical LPF 118 and the CCD 117 are fittedfrom the back. In this case, the front circumferential edge of theoptical LPF 118 contacts the stepped part 147 in a virtually airtightfashion. Thus, the optical LPF 118 is held by the stepped part 147 at aspecific position in the direction of the photographic optical axis. Theoptical LPF 118 is therefore prevented from slipping forwards from theholder 145. The level of airtight sealing between the CCD 117 and theoptical LPF 118 is sufficient to prevent dust from entering to form animage having shadows of dust particles. In other words, the sealinglevel need not be so high as to completely prevent the in-flow ofgasses.

On the front circumferential edge of the holder 145, a dust-filterholding unit 148 is provided, covering the entire front circumferentialedge of the holder 145. The dust-filter holding unit 148 is formed,surrounding the stepped part 147 and projecting forwards from thestepped part 147, in order to hold the dust filter 119 in front of theLPF 118 and to space the filter 119 from the stepped part 147 by apredetermined distance. The opening of the dust-filter holding unit 148serves as focusing-beam passing area 149. The dust filter 119 is shapedlike a polygonal plate as a whole (a square plate, in this embodiment).The dust filter 119 is supported on a seal 150 (a support member),pushed onto the seal 150 by a pushing member 151 which is constituted byan elastic body such as a leaf spring and has one end fastened withscrews 152 to the dust-filter holding unit 148. More specifically, acushion member 153 made of vibration attenuating material, such asrubber or resin, and adhered to the pushing member 151, is interposedbetween the pushing member 151 and the dust filter 119. On the otherhand, at the back of the dust filter 119, the seal 150 having anring-shaped lip part 150 a surrounding the center of the dust filter 119is interposed between the circumferential part of the dust filter 119and the dust-filter holding unit 148. The pushing member 151 exerts apushing force, which bends the lip part 150 a. The lip part 150 a pushesthe dust filter 119. As a result, the space including the opening 146 issealed airtight and the dust filter 119 is supported.

The dust filter 119 is positioned with respect to the Y-direction in theplane that is perpendicular to the optical axis, as that part of thepushing member 151 which is bent in the Z-direction, receive a forcethrough a positioning member 154. Or the other hand, the dust filter 119is positioned with respect to the X-direction in the plane that isperpendicular to the optical axis, as a support part 155 provided on theholder 145 receive a force through the positioning member 154, as isillustrated in FIG. 2B. The positioning member 154 is made ofvibration-attenuating material such as rubber or resin, too, not toimpede the vibration of the dust filter 119. The main body 150 b of theseal 150 is pressed onto the outer circumferential edge of a ring-shapedprojection 145 a fitted at the rim of the opening 146 of the holder 145,and is thereby set in place.

When the dust filter 119 receives gravitational acceleration G and anexternal force (such as an inertial force) as the camera is moved, theexternal force is applied to the pushing member 151 or the seal 150. Thepushing member 151 is a plate made of phosphor bronze or stainlesssteel, either for use as material of springs, and has high flexuralrigidity. By contrast, the seal 150 is made of rubber and has smallflexural rigidity. Thus, the seal 150 is deformed due to the externalforce.

Cushion members 156 (second support members) made of vibrationattenuating material, such as rubber or soft resin, are provided on thatsurface of the dust-filter holding unit 148, which faces the back of thedust filter 119. At least two cushion members 156 (four cushion membersin this embodiment) are positioned, almost symmetric with respect to theoptical axis, and, are spaced by distance ΔZ from the dust filter 119 inthe direction of the optical axis. When the seal 150 is deformed by thedistance ΔZ, the dust filter 119 contacts the cushion member 156. As aresult, the external force tends to compress the cushion member 156 (atfour parts). However, the cushion member 156 is scarcely deformeddespite the external force, because its compression rigidity is higherthan the flexural rigidity of the seal 150. Therefore, the seal 150 isdeformed, but very little. Note that the cushion member 156 is arranged,supporting the dust filter 119 at the nodes where the dust filter 119scarcely undergoes vibration even if the dust filter 119 is pushed bythe cushion member 156. Since the cushion member 156 is arranged so, thevibration of the dust filter 119 is not much impeded. This helps toprovide a dust-screening mechanism having that generate vibration atlarge amplitude and hence can remove dust at high efficiency. Moreover,the deformation of the seal 150, caused by the external force, is assmall as ΔZ (for example, 0.1 to 0.2 mm). Hence, an excessively largeforce will not applied to the seal 150 to twist the seal 150, failing tomaintain the airtight state, or the seal 150 will not contact the dustfilter 119 with an excessive pressure when the external force isreleased from it.

The seal 150 may of course have its main body 150 b secured to theholder 145 by means of, for example, adhesion. If the seal 150 is madeof soft material such as rubber, it may be secured to the dust filter119. In this case, the seal 150 only needs to apply a pressing forcelarge enough to support the vibrator configured by the dust filter 119and the piezoelectric elements 120 a and 120 b. Assume that the vibratorhas a mass of several grams (e.g., less than 10 g (=0.01 kg). Then, inorder to support the vibrator even while the digital camera 10 remainsdirected in horizontal direction, upward in vertical direction ordownward in vertical direction, the vibrator must withstand at least 2G, where G is the gravitational acceleration (=9.81 m/s²). It issufficient for the vibrator to withstand several times to ten times 2 G.In this case, the pushing force the seal 150 should exert is as small as0.01×10×9.81≈1 N (Newton). If the pushing force is so small, the seal150 would not suppress the vibration of the dust filter 119.

Moreover, as shown in FIG. 2B, the lip part 150 a of the seal 150 isshaped like a ring, arced at the four corners and having no inflectionpoints. So shaped, the lip part 150 a is not locally deformed when itreceives an external force.

The image acquisition unit 116 is thus configured as an airtightstructure that has the holder 145 having a desired size and holding theCCD 117. The level of airtight sealing between the dust filter 119 andthe dust-filter holding unit 148 is sufficient to prevent dust fromentering to form an image having shadows of dust particles. The sealinglevel need not be so high as to completely prevent the in-flow ofgasses.

As shown in FIG. 3 and FIG. 4, the piezoelectric element 120 a has twosignal electrodes 157 a and 158 a, and the piezoelectric element 120 bhas two signal electrodes 157 b and 158 b.

The signal electrodes 158 a and 159 b, which constitute a non-vibratingpart, are electrically connected to the electrodes (back electrodes)provided respectively on the hacks of the piezoelectric elements 120 aand 120 b, which face the dust filter 119. The back electrodes areelectrically connected to the ground of the dust filter control circuit121, too. Therefore, no electrical signals are supplied to the backelectrodes to contracting and expanding the piezoelectric elements 120 aand 120 b. The back electrodes electrically connected to the ground maynot be electrically connected to the signal electrodes 158 a and 158 b.That is, the signal electrodes 158 a and 158 b may not be electricallyconnected to the ground. (i.e., same potential), making it possible tosupply electrical signals to the signal, electrodes 159 a and 159 b. Inthis case, the signal electrodes 158 a and 159 b can function as anon-vibrating part if they are not supplied with electrical signals.This is why the above-mentioned configuration is possible. Even if thesignal electrodes 158 a and 158 b can receive electrical signals, thoseparts of the piezoelectric elements 120 a and 120 b, which correspond tothe signal electrodes 158 a and 158 b, will not function as vibratorsunless they are “polarized.” This configuration is also possible.

On the other hand, the signal electrodes 157 a and 157 b, whichconstitute vibration application parts, receive a voltage (electricalsignal for expanding and contracting the piezoelectric elements) of afrequency determined by the dimensions and materials of the dust filter119 and piezoelectric elements 120 a and 120 b, from the dust filtercontrol circuit 121 that is a drive unit. The vibration applicationparts of the piezoelectric elements 120 a and 120 b, which areinterposed between the signal electrodes 157 a and 157 b, one the onehand, and the back electrodes, on the other, expand and contract,vibrating the dust filter 119. Dust is thereby removed from the surfaceof the dust filter 119. As shown in FIG. 2B, the signal electrodes 157 aand 157 b, which constitute the vibration application unit of thevibrator 159, are arranged, having unbalance along the long sides of thepiezoelectric elements 120 a and 120 b, each shaped like a long and thinrectangle.

The signal electrodes 157 a, 157 b, 158 a and 158 b are electricallyconnected to the electrode terminals 160 a, 160 b, 160 c and 160 d,which are provided on a flexible printed board 160 (hereinafter referredto as “flex”). When a specific electrical signal is input from the dustfilter control circuit 121 to the vibration application parts of thepiezoelectric elements 120 a and 120 b, the piezoelectric elements 120 aand 120 b vibrate, which are arranged symmetrically with respect to thesymmetry axis of the dust filter 119 (the symmetry axis of the dustfilter 119 is a virtual axis at almost the same distance from thepiezoelectric elements 120 a and 120 b). The piezoelectric elements 120a and 120 b are arranged symmetrically to the symmetry axis of the dustfilter 119 and so shaped to vibrate at a large amplitude as will beexplained later.

The flex 160 further has test terminals 160 e, 160 f and 160 f, leadterminals 160 h and 160 i, and connection terminals 160 j and 160 k. Theconnection terminals 160 j and 160 k have yet to be connected to eachother at the time of testing the vibrator 159. The connection terminals160 j and 160 k are connected to each other by soldering after thevibrator 156 is evaluated as good and before the dust filter 119 isincorporated into the product. Before the connection terminals 160 j and160 k are connected to each other, either the conductive patternprovided between the connection terminal 160 j and the electrodeterminal 160 a or the conductive pattern provided between the connectionterminal 160 k and the electrode terminal 160 c constitutes a firstcircuit that inputs an electrical signal to one of the two vibrationapplication units. The other conductive pattern constitutes a secondcircuit that outputs an electrical signal that the other vibrationapplication unit generates from the vibration generated when anelectrical signal is input to the first circuit. Hence, the connectionterminals 160 j and 160 k constitute a connection unit whichelectrically connects the first and second circuits. The dust filtercontrol circuit 121 cooperates with the Bucom 101, and can function as adrive unit that drives both vibration application units while the firstand second circuits remain connected by the connection terminals 160 jand 160 k as the connection unit.

The vibration application units of the piezoelectric elements 120 a and120 b are asymmetrical with respect to the nodes of standing-wavebending vibration as will be specifically described later. If a specificelectrical signal is applied between the test terminals 160 e and 160 f,standing-wave bending vibration occurs, generating a voltage. Thevibration (i.e., voltage equivalent to the vibrational frequency andamplitude) can therefore be detected.

The electrode terminals 160 a and 160 b of the flex 160 are made ofresin and supper etc., and have flexibility. Therefore, they littleattenuate the vibration of the vibrator 159 including the piezoelectricelements 120 a and 120 b. The piezoelectric elements 120 a and 120 b areprovided at positions where the vibrational amplitude is small (at thenodes of vibration, which will be described later), and can thereforesuppress the attenuation of vibration. The piezoelectric elements 120 aand 120 b move relative to the body unit 100 if the camera 10 has such ahand-motion compensating mechanism as will be later described. Hence, ifthe dust filter control circuit 121 is held by a holding member formedintegral with the body unit 100, the electrode terminals 160 a and 160 bof the flex 160 and lead lines 161 a and 161 b connected to the flex 160are deformed and displaced as the hand-motion compensating mechanismoperates. The electrode terminals 160 a and 160 b of the flex 160 do nothinder the operation of the hand-motion compensating mechanism, becausethey are flexible and thin as described above. Moreover, the lead lines161 a and 161 b do not hinder the operation of the hand-motioncompensating mechanism, either, because they can flex in any directions.

In the present embodiment, the flex 160 has a simple structure, havingelectrode terminals 160 a and 160 b formed integral with, and led from,the piezoelectric elements and 120 b, respectively. The flex 160 issimple also in that its lead terminals 160 h and 160 i formed integralare connected to the dust filter control circuit 121 by the lead lines161 a and 161 b, respectively. The flex 160 can therefore be made smalland light, and is therefore best fit for use in cameras having ahand-motion compensating mechanism.

The dust removed from the surface of the dust filter 119 falls onto thebottom of the body unit 100, by virtue of the vibration inertia and thegravity. In this embodiment, a base 162 is arranged right below the dustfilter 119, and holding members 163 a and 163 b made of, for example,adhesive tape, is provided on the base 162. The holding members 163 aand 163 b reliably trap the dust fallen from the dust filter 119,preventing the dust from moving back to the surface of the dust filter119.

The hand-motion compensating mechanism will be explained in brief. Asshown in FIG. 1, the hand-motion compensating mechanism is composed ofan X-axis gyro 164, a Y-axis gyro 165, a vibration control circuit 166,an X-axis actuator 167, a Y-axis actuator 168, an X-frame 169, a Y-frame170 (holder 145), a position sensor 172, and an actuator drive circuit173. The X-axis gyro 164 detects the angular velocity of the camera whenthe camera moves, rotating around the X axis. The Y-axis gyro 165detects the angular velocity of the camera when the camera rotatesaround the Y axis. The vibration control circuit 166 calculates a valueby which to compensate the hand motion, from the angular-velocitysignals output from the X-axis gyro 164 and Y-axis gyro 165. Inaccordance with the hand-motion compensating value thus calculated, theactuator drive circuit 173 moves the CCD 117 in the X-axis direction andY-axis direction, which are first and second directions orthogonal eachother in the XY plane that is perpendicular to the photographic opticalaxis, thereby to compensate the hand motion, if the photographic opticalaxis is taken as Z axis. More precisely, the X-axis actuator 167 drivesthe X-frame 169 in the X-axis direction upon receiving a drive signalfrom the actuator drive circuit 173, and the Y-axis actuator 168 drivesthe Y-frame 170 in the Y-axis direction upon receiving a drive signalfrom the actuator drive circuit 173. That is, the X-axis actuator 167and the Y-axis actuator 168 are used as drive sources, the X-frame 169and the Y-frame 170 (holder 145) which holds the CCD 117 of the imageacquisition unit 116 are used as objects that are moved with respect tothe frame 171. Note that the X-axis actuator 167 and the Y-axis actuator168 are each composed of an electromagnetic motor, a feed screwmechanism, and the like. Alternatively, each actuator may be a linearmotor using a voice coil motor, linear piezoelectric motor or the like.The position sensor 172 detects the position of the X-frame 169 and theposition of the Y-frame 170. On the basis of the positions the positionsensor 172 have detected, the vibration control circuit 166 controls theactuator drive circuit 173, which drives the X-axis actuator 167 and theY-axis actuator 168. The position of the CCD 117 is thereby controlled.

In the hand-motion compensating mechanism so configured as describedabove, the dust filter 119 is driven together with the CCD 117. The dustfilter 119 should therefore have a small mass. Further, the electricalconnection member connecting the flex 160 and the vibration controlcircuit 166 should have a small mass, too, and should have but a smallload while operating. In this embodiment, the flex 160 has connectionterminals (i.e., lead terminals 160 h and 160 i) in the smallest numberpossible. The number of lead lines 161 a and 161 b, which electricallyconnect the flex 160 the vibration control circuit 166, can therefore bereduced to a minimum. This helps to reduce the mass of the electricalconnection members, ultimately decreasing the load generated as theterminals are deformed while the hand-motion compensating mechanism isoperating.

The dust removal mechanism of the first embodiment will be described indetail, with reference to FIGS. 3 to 15. The dust filter 119 has atleast one side symmetric with respect to a certain symmetry axis, and isa glass plate (optical element) of a polygonal plate as a whole (asquare plate, in this embodiment). The dust filter 119 has a regionflaring in the radial direction from the position at which maximumvibrational amplitude is produced. This region forms a transparent part.Alternatively, the dust filter 119 may be D-shaped, formed by cutting apart of a circular plate, thus defining one side. Still alternatively,it may formed by cutting a square plate, having two opposite sidesaccurately cut and having upper and lower sides. The above-mentionedfastening mechanism fastens the dust filter 119, with the transparentpart opposed to the front of the LPF 118 and spaced from the LPF 118 bya predetermined distance. To one surface of the dust filter 119 (i.e.,back of the filter 119, in this embodiment), the piezoelectric elements120 a and 120 b, which are vibrating members, are secured at the upperand lower edges of the filter 119, by means of adhesion using adhesive.The piezoelectric elements 120 a and 120 b, which are arranged on thedust filter 119, constitute the vibrator 159. The vibrator 159 undergoesresonance when a voltage of a prescribed frequency is applied to thepiezoelectric elements 120 a and 120 b. The resonance achieves suchtwo-dimensional bending vibration of a large amplitude, as illustratedin FIGS. 5A to 5D, FIG. 7B, FIG. 8 and FIG. 9.

As shown in FIG. 3, signal electrodes 157 a and 158 a are formed on thepiezoelectric element 120 a, and signal electrodes 157 b and 158 b areformed on the piezoelectric element 120 b. Note that the hatched partsshown in FIG. 3 show the shapes of the signal electrodes clearly, not toillustrating the sections thereof. The signal electrodes 158 a and 158 bare provided on the back opposing the signal electrodes 157 a and 157 b,and are bent toward that surface of the piezoelectric element 120 a, onwhich the signal electrodes 157 a and 157 b are provided. The flex 160having the above-mentioned conductive pattern is electrically connectedto the signal electrodes 157 a and 158 a and to the signal electrodes157 b and 158 b. To the signal electrodes 157 a, 157 b, 158 a and 158 b,a drive voltage of the prescribed frequency is applied form the dustfilter control circuit 121 through flex 160. When this drive voltage isapplied to the vibration application units of the piezoelectric elements120 a and 120 b expand and contract in accordance with the drivevoltage. The dust filter 119 is thereby forcedly vibrated. The bending,propagating wave transiently generated by the forced vibration isreflected at the edges of the dust filter 119, and is eventuallysuperimposed, for a predetermined time, on the propagating wavecontinuously generated. As a result, there can be generated such atwo-dimensional, standing-wave bending vibration as is shown in FIGS. 5Ato 5D. The flex 160 shown in FIG. 4 has more terminals than the flexshown in FIG. 2B. Therefore, connection terminals 174 a and 174 b and atest terminal 175 are provided on the conductive pattern that connectsthe electrode terminals 160 a and 160 b.

The dust filter 119 is dimensioned such that the long sides are oflength LA and the short sides are of length LB orthogonal to the longsides. (This size notation accords with the size notation used in FIG.6.) Since the dust filter 119 shown in FIG. 5A is rectangular, it isidentical in shape to the “virtual rectangle” according to thisinvention (later described). Hence, the long sides LA of the dust filter119 are identical to the sides LF of the virtual rectangle that includethe sides LA. The bending vibration shown in FIGS. 5A to 5D is standingwave vibration. As seen from FIG. 5A, the vibrational amplitude is notperfectly zero (0) in the node area (i.e., area where the vibrationalamplitude is small) 176 indicated by a thin solid line. Rather, thevibrational amplitude is small at any position where the nodes, forexample, intersect with one another. This characterizes the presentembodiment. Note that the meshes shown in FIG. 5A are division meshesusually used in the final element method.

If the node areas 176 are at short intervals as shown in FIG. 5A whenthe vibration speed is high, in-plane vibration (vibration along thesurface) will occur in the node areas 176. This vibration induces alarge inertial force in the direction of the in-plane vibration (seemass point Y2 in FIG. 15, described later, which moves over the nodealong an arc around the node, between positions Y2 and Y2′) to the dustat the node areas 176. If the dust filter 119 is inclined to becomeparallel to the gravity so that a force may act along the dust receivingsurface, the inertial force and the gravity can remove the dust from thenode areas 176.

The area between the nodes shown in FIG. 5A is an antinode area having alarge vibrational amplitude. In this antinode area, the peaks andvalleys of waves alternately appear at different times. In FIG. 5A, thinbroken lines indicate the ridges 177 of the wave peaks. The dustadhering to the antinode area is removed because of the inertial forceexerted by the vibration. The dust can be removed from the node areas176, too, by producing vibration in another mode (for example, thevibrational mode illustrated in FIG. 9), at similar amplitude at eachnode area 176 in FIG. 5A.

In the FIGS. 5A to 5D, reference number 178 indicates a vibrationapplication part, reference numbers 179 indicates the centerline of thevibration application unit 178, reference number 180 indicates anon-vibrating part, and reference number 181 indicates a non-electrodepart, and reference number 182 indicates a maximum amplitude regionwhere the maximum amplitude is attained.

The bending vibrational mode shown in FIGS. 5A to 5D is achieved bysynthesizing the bending vibration of the X-direction and the bendingvibration of the Y-direction. The fundamental state of this synthesis isshown in FIG. 7A. If the vibrator 159 is put on a member that littleattenuates vibration, such as a foamed rubber block, and then made tovibrate freely, a vibrational mode of producing such lattice-shaped nodeareas 176 as shown in FIG. 7B will be usually attained easily. In thefront view included in FIG. 7A, the broken lines define the centers ofthe node areas 176 shown in FIG. 7B (more precisely, the lines indicatethe positions where the vibrational amplitude is minimal in thewidthwise direction of lines). In this case, a standing wave, bendingvibration at wavelength λ_(x) occurs in the X-direction, and a standingwave, bending vibration at wavelength λ_(y) occurs in the Y-direction.These standing waves are synthesized as shown in FIG. 7B. With respectto the origin (x=0, y=0), the vibration Z(x, y) at a given point P(x, y)is expressed by Equation 1, as follows:Z(x,y)=A·W _(mn)(x,y)·cos(γ)+A·W _(nm)(x,y)·sin(γ)  (1)where A is amplitude (a fixed value here, but actually changing with thevibrational mode or the power supplied to the piezoelectric elements); mand n are positive integers including 0, indicating the order of naturalvibration corresponding to the vibrational mode; γ is a given phaseangle;

${{W_{mn}\left( {x,y} \right)} = {{\sin\left( {{n\;{\pi \cdot x}} + \frac{\pi}{2}} \right)} \cdot {\sin\left( {{m\;{\pi \cdot y}} + \frac{\pi}{2}} \right)}}};\mspace{14mu}{and}$${W_{nm}\left( {x,y} \right)} = {{\sin\left( {{m\;{\pi \cdot x}} + \frac{\pi}{2}} \right)} \cdot {{\sin\left( {{n\;{\pi \cdot y}} + \frac{\pi}{2}} \right)}.}}$

Assume that the phase angle γ is 0 (γ=0). Then, Equation 1 changes to:

$\begin{matrix}{{Z\left( {x,y} \right)} = {A \cdot {W_{mn}\left( {x,y} \right)}}} \\{= {A \cdot {\sin\left( {\frac{n \cdot \pi \cdot x}{\lambda_{x}} + \frac{\pi}{2}} \right)} \cdot {{\sin\left( {\frac{m \cdot \pi \cdot y}{\lambda_{y}} + \frac{\pi}{2}} \right)}.}}}\end{matrix}$

Further assume that λ_(x)=λ_(y)=λ=1 (x and y are represented by the unitof the wavelength of bending vibration). Then:

$\begin{matrix}{{Z\left( {x,y} \right)} = {A \cdot {W_{mn}\left( {x,y} \right)}}} \\{= {A \cdot {\sin\left( {{n \cdot \pi \cdot x} + \frac{\pi}{2}} \right)} \cdot {{\sin\left( {{m \cdot \pi \cdot y} + \frac{\pi}{2}} \right)}.}}}\end{matrix}$

Similarly, if γ=π/2, too, the front term of the equation (1) will bezero. Hence, a similar standing wave is generated. FIG. 7A shows thevibrational mode that is applied if m=n (since the X-direction vibrationand the Y-direction vibration are identical in terms of order andwavelength, the dust filter 119 has a square shape). In this vibrationalmode, the peaks, nodes and valleys of vibration appear at regularintervals in both the X-direction and the Y-direction, and vibrationnode areas 176 appear as a checkerboard pattern (conventionalvibrational mode). In the vibrational mode where m=0, n=1, the vibrationhas peaks, nodes and valleys parallel to a side (LB) that extendsparallel to the Y-direction. In the vibrational mode described above,the X-direction vibration and the Y-direction vibration are generated,independent of each other. Even if the X-direction vibration and theY-direction vibration are synthesized, the amplitude of vibration (orvibration speed) will have the same value as in the case where onlyX-direction vibration is generated (forming nodes and peaks and valleys,all parallel to the side LB) or the case where only Y-directionvibration is generated (forming nodes and peaks and valleys, allparallel to the side LA). This takes place, also in the vibration modeshown in FIG. 7B. In these vibrational modes, the phase angle γ is k×π/2(γ=k×π/2) as pointed out before, if k is 0 or an integer (eitherpositive or negative). That is, in these vibrational modes, cos γ andsin γ are 0.

A vibrational mode in which the phase angle γ has a different value willbe explained. In view of this, the dust filter 119 may be elongated alittle, shaped like a rectangle, and may be vibrated at a specificfrequency, or in a mode where m=3 and n=2. In this vibrational mode, thephase angle γ is +π/4 or ranges from −π/4 to −π/8. This vibrational modeis a mode in which the present embodiment will have very largevibrational amplitude (the maximum amplitude at the same level as at theconventional circular dust filter). If γ=+π/4, the vibrational mode willbe the mode shown in FIGS. 5A to 5D. In this vibrational mode, a closedcurve is defined by the peak ridges 177 of the vibrational amplitude,which is plane-symmetrical with respect to the midpoint on the opticalaxis (i.e., point at which the above-mentioned virtual symmetry axisintersects with a virtual, centerline later described), though the dustfilter 119 is rectangular. Consequently, a reflected wave coming from aside extending in the X-direction and a reflected wave coming from aside extending in the Y-direction are efficiently combined, forming astanding wave. FIG. 8 shows a vibrational mode in which γ=−π/4 and whichis achieved by changing the vibrational frequency of the dust filter 119of FIGS. 5A to 5D. In this vibrational mode, peak ridges 177 ofvibrational amplitude are formed, surrounding the midpoint of each side.That is, the center of the dust filter 119 becomes a node area 176 wherevibrational amplitude is scarcely observed. Peak ridges 177 ofvibrational amplitude are formed, surrounding the midpoint of each side.

FIG. 9 shows the vibrational mode shown in FIGS. 5A to 5D, in whichvibration is generated almost in the conventional vibrational modewherein the peaks of vibration are parallel to the sides of thepiezoelectric elements. The vibrational mode shown in FIG. 9 can beachieved by changing the dust filter 119 and piezoelectric elements 120a and 120 b in configuration (e.g., aspect ratio of the dust filter 119,as described later) in order to increase or decrease the phase anglefrom +π/4.

The dust filter 119 of the vibrator 159, shown in FIG. 5A, is a glassplate (optical element) having a size of 30.8 mm (X-direction: LA,LF)×28.5 mm (Y-direction: LB)×0.65 mm (thickness). The dust filter 119is rectangular, having long sides LA (30.8 mm, extending in theX-direction) and short sides LB (28.5 mm). Therefore, the dust filter119 is identical to the “virtual rectangle” according to this invention,which has the same area as the dust filter 119. The long sides LA of thedust filter 119 are arranged are thus identical to the sides LF of thevirtual rectangle that includes the sides LA. The piezoelectric elements120 a and 120 b are made of lead titanate-zirconate ceramic and have asize of 21 mm (X-direction: LP)×3 mm (Y-direction)×0.8 mm (thickness).The piezoelectric elements 120 a and 120 b are adhered with epoxy-basedadhesive to the dust filter 119, extending along the upper and lowersides of the filter 119 (optical element), respectively. Morespecifically, the piezoelectric elements 120 a and 120 b extend in theX-direction and arranged symmetric in the left-right direction, withrespect to the centerline of the dust filter 119, which extends in theY-direction. In this case, the resonance frequency in the vibrationalmode of FIG. 5A is in the vicinity of 91 kHz. At the center of the dustfilter 119, a maximal vibration speed and vibrational amplitude can beattained if the dust filter is shaped like a circle in which therectangular dust filter 119 is inscribed. The vibration-speed ratio hassuch a value as shown in FIG. 10, the maximum value of which is 1.000.In the graph of FIG. 10, the line curve pertains to the case where thepiezoelectric elements 120 a and 120 b are arranged parallel to the longsides of the dust filter 119, and the dots pertain to the case where the120 a and 120 b are arranged parallel to the short sides of the dustfilter 119. In this vibrational mode, the piezoelectric elements 120 aand 120 b should better be arranged at the longer sides of the dustfilter 119. A higher vibration speed can be achieved than otherwise.

As described above, the phase angle γ is +π/4 or ranges from −π/4 to−π/8. Nevertheless, the phase angle need not have such a precise value.If the phase angle γ differs a little from such value, the vibrationalamplitude can be increased. Even in the vibrational mode of FIG. 9, inwhich the phase angle γ is a little smaller than +π/4, the peak ridges177 of vibrational amplitude form closed loops around the optical axis,too, and the vibration speed decreases in the Z-direction at the centerof the vibrator 159. This dust filter 119 is a glass plate (opticalelement) that has a size of 30.8 mm (X-direction: LA, LF)×28.5 mm(Y-direction: LB)×0.65 mm (thickness). The dust filter 119 isrectangular, having long sides LA (30.8 mm, extending in theX-direction) and short sides LB (28.5 mm). Therefore, the dust filter119 is identical to the “virtual rectangle” according to this invention,which has the same area as the dust filter 119. The piezoelectricelements 120 a and 120 b have a size of 30 mm (X-direction)×3 mm(Y-direction) 0.8 mm (thickness), having a length almost equal to thelength LF (in the X-direction) of the dust filter 119, and are made oflead titanate-zirconate ceramic. The piezoelectric elements 120 a and120 b are adhered with an epoxy-based adhesive to the dust filter 119,extending along the upper and lower sides of the filter 119,respectively, and positioned symmetric in the X-direction with respectto the centerline of the dust filter 119. In this case, the resonancefrequency in the vibrational mode shown in FIG. 9 is in the vicinity of68 kHz. As in FIGS. 2A and 2B, in this case, too, the dust filter 119 issupported by the lip part 150 a of the seal 150, and the holder 145 hasfour cushion members 156, which act as second support members if anexternal force is applied to the seal 150.

The vibrator 159 of this configuration may not achieve a targetvibration speed. The vibrator 159 may therefore fail to achieve asufficient dust removal efficiency, depending on the material, shape andassembling deviation of the vibrator 159 and the material, shape,supporting position and supporting force of the supporting unit. To testthe vibrator 159 during the manufacture or repairing process, the dustfilter control circuit 121 may be used to vibrate the dust filter 119and a laser Doppler speedometer may be used to measure the vibrationspeed of the dust filter 119. However, the vibration speed cannot bemeasured unless a light reflecting tape, for example, is adhere to thedust filter 119, because the vibration surface of the dust filter 119 istransparent. Further, the vibrational amplitude greatly changes inaccordance with the vibrational mode and the position of the dust filter119, as shown in FIGS. 5A to 5D. Therefore, the dust filter 119 must beprecisely positioned to measure its vibration speed. Therefore, thevibration speed cannot easily be measured with the laser Dopplerspeedometer. The use of the laser Doppler speedometer during themanufacture requires a high cost and much labor. Hence, the laserDoppler speedometer can hardly be employed.

This is why a piezoelectric element may be provided, on the dust filterto detect the vibration as described above, or two piezoelectricelements may be provided on a rectangular dust filter as in thisembodiment. In the latter case, an electrical signal is supplied to onepiezoelectric element, and the vibration of the dust filter is detectedby the other piezoelectric element.

A detection piezoelectric element, if provided on a part of eitherpiezoelectric element, hinders the vibration of the dust filter 119 andrenders the vibrator large. If the detection piezoelectric element issmall in order not to make the vibrator large, it cannot accuratelydetect the vibration of the dust filter, depending on the position whereit is arranged. In addition, if the detection piezoelectric element hasa trouble, it will erroneously determine that abnormality has developedin the vibrator.

By contrast, the technology of using two piezoelectric elements cannotdetect the vibrational amplitude that reflects the vibrational state ofthe dust filter if the vibrational state is symmetrical to the dustfilter and complex as in the present embodiment.

In the present embodiment, the piezoelectric elements 120 a and 120 bare configured to assume weight balance with respect to not only thevirtual symmetry axis at the same distance from the piezoelectricelements 120 a and 120 b, but also the virtual centerline connecting thegravity centers of the piezoelectric elements 120 a and 120 b. Thevibration application part 178 is arranged asymmetrical to the virtualcenterlines of the piezoelectric elements 120 a and 120 b. Therefore,the vibrational amplitude of the vibration application part 178 will beasymmetrical to the centerline of the vibration application part ifvibration symmetrical to the virtual centerline is generated. (Thecenterline of the vibration application part is perpendicular to thevirtual symmetry axis, bisects the surface area of the vibrationapplication part 178 into equal halves, and is the axis of vibration.)

More specifically, in the case of FIGS. 5A to 5D, X3, X4 and X5 arevibrational regions in the signal electrodes 157 a and 157 b,respectively, which correspond to the vibration application parts 179.In the vibrational regions X3 and X5, the vibration application partvibrates in the same phase. X4 is a vibrational region, in which thevibration application part vibrates in the opposite phase. If one of thepiezoelectric elements detects the vibration of the dust filter 119, apositive electrical charge is generated in the vibrational regions X3and X5 and a negative electrical charge is generated in the vibrationalregion X4, or other way around. Nonetheless, these charges generated donot completely cancel out one another, because the vibration applicationpart 178 is so formed that its vibrational amplitude is asymmetrical toits own centerline as described above. Thus, the electrical chargeremains in part, resulting in a voltage that corresponds to thevibrational amplitude in the vibrational regions X3, X4 and X5.

FIG. 11 shows the relation between the voltages detected in a pluralityof dust filters, each generated at piezoelectric element 120 a, and thevibration speed ratio detected at the center part of any dust filter 119when an electrical signal is supplied from the dust filter controlcircuit 121 to both piezoelectric elements 120 a and 120 b. (Thevibration speed ratio is a ratio of vibration speed V at arbitrary stateto vibration speed V0 at which dust filter must be vibrated to removedust from it.) Note that the voltage detected pertains to the vibrationgenerated in each dust filter 119 and detected by a vibration detector184 of FIG. 12, according to this embodiment, in the vibrational stateof FIG. 9. As shown in FIG. 12, the vibration detector 184 has a dustfilter drive circuit 184A and a voltage detection circuit 184B. The dustfilter drive circuit 184A is connected to the first circuit andconfigured to supply an electrical signal to the piezoelectric elementof the first circuit, i.e., piezoelectric element 120 b in this case.The voltage detection circuit 184B is connected to the second circuitand configured to detect the voltage generated across the piezoelectricelement of the second circuit, i.e., piezoelectric element 120 a in thiscase.

As described above and as shown in FIG. 2A and FIG. 2B, thepiezoelectric elements 120 a and 120 b are arranged symmetrically withrespect to the dust filter 119. (The piezoelectric elements 120 a and120 b assume weight balance with respect to not only the virtualsymmetry axis, but also the virtual centerline.) Further, thepiezoelectric elements 120 a and 120 b are identical in shape. Thevibration generated at the dust filter 119 is therefore symmetrical(with respect to the plane containing the virtual centerline and beingperpendicular to the virtual symmetry axis).

Vibration is generated in the vibrational regions X3 and X5 in the samephase, and vibration is generated in the vibrational region X4 in theopposite phase. The vibrational regions X3, X4 and X5 have the samearea. A positive electrical charge is generated in the vibrationalregions X3 and X5 and a negative electrical charge is generated in thevibrational region X4, or other way around. Therefore, the electricalcharges seem to cancel out each other to generate no voltage at all.Nonetheless, the vibrational amplitude is the largest in the vibrationalregion X3, has a medium value in the vibrational region X4, and is thesmallest in the vibrational region X5. The total electrical chargegenerated because of the vibration does not become zero. Thus, thevoltage detected at the piezoelectric elements is not zero also in theembodiment of FIG. 9. This is because the vibrational amplitude isasymmetrical with respect the centerline of the vibration applicationpart. The amplitude of the vibration generated can therefore beaccurately detected.

Vibrational nodes may be generated, which, are parallel to each side ofthe rectangular dust filter 119 (see FIG. 7A and FIG. 7B). In this case,the total electrical charge the vibration generates at the vibrationapplication part will become zero if the centerline 179 of the vibrationapplication part 178 is aligned with a node of vibration. As a result,the vibration of the dust filter 119 cannot be detected at all. If thepiezoelectric element vibrated or the piezoelectric element used todetect vibration has a trouble, the electrical signal detected has a lowlevel. Thus, the detected electrical signal correctly reflects theamplitude of the vibration generated when electrical signals are inputto both piezoelectric elements of the product.

In the vibrational state (vibrational mode) of FIG. 11, resonationoccurs at a frequency near 93 kHz. The voltage detected is collated withthe vibration speed ratio. The speed of the vibration generated at thedust filter 119 when an electrical signal is supplied to bothpiezoelectric elements in the detection method according to thisembodiment can therefore be accurately predicted. Hence, the vibrationdetector 184 can easily determine whether the vibrator 159 composed ofthe dust filter 119, piezoelectric elements 120 a and 120 b and flex 160is a good one or a defective one. Moreover, the product shown in FIG. 25can be inspected to be a good one or a defective one with regard towhether the dust filter 119 is duly held in the product.

The dust filter 119 has a vibrational mode at a frequency near 82 kHz,too. The voltage detected in the vibrational mode of 93 kHz is collatedwith the vibration speed ratio in the vibrational mode of 82 kHz, in thesame manner as in the case shown in FIG. 11. Therefore, once thevibration speed is detected in one vibrational mode, the vibration speedin any other vibrational mode can be predicted.

In the vibrational state of FIG. 7B, vibrational regions X1 and X2 areopposite in terms of vibrational phase and are almost identical in termsof vibrational amplitude. Also in the vibrational state of FIG. 7B, thevibrational amplitude is asymmetrical with respect to the centerline ofthe vibration application part 178. The vibrational state, including theamplitude of the vibration generated at the dust filter 119, canaccurately detected from the voltage detected at the vibrationapplication part 178. In the vibrational state of FIG. 8B, too, thevibrational regions X2 and X3 are opposite in terms of vibrationalphase, and the vibrational amplitude in the vibrational region X2 islarger than that in the vibrational region X3. Also in this vibrationalstate, the vibrational amplitude is asymmetrical, with respect to thecenterline of the vibration application part 178, and can be accuratelydetected, along with the amplitude of the vibration generated at thedust filter 119.

FIG. 13 shows a modification of the vibrator 159. The modified vibrator159 has a dust filter 119 that is D-shaped, formed by cutting a part ofa plate shaped like a disc, thus defining one side. That is, themodified vibrator 159 uses a D-shaped dust filter 119 that has a sidesymmetric with respect to the symmetry axis extending in theY-direction. The piezoelectric element 120 a is arranged on the surfaceof the dust filter 119, extending parallel to that side and positionedsymmetric with respect to the midpoint of the side (or to a symmetryaxis extending in the Y-direction). On the other hand, the piezoelectricelement 120 b is substantially inscribed in the outer circumference ofthe dust filter 119 and extends parallel to that side of the dust filter119. So shaped, the dust filter 119 is more symmetric with respect toits center (regarded as the centroid), and can more readily vibrate in astate shown in FIGS. 5A to 5D. In addition, the dust filter 119 can besmaller than the circular one.

This embodiment has two piezoelectric elements 120 a and 120 b, whichare identical in shape. The piezoelectric, elements 120 a and 120 b areconnected by a flex 160. The flex 160 has a conductive pattern. Theconductive pattern is so formed to be electrically connected to thepiezoelectric elements 120 a and 120 b, or to electrically connect thepiezoelectric elements 120 a and 120 b in parallel (see FIG. 3 and FIG.4).

Further, the dust filter 119 may have a shape asymmetrical (tovibration), as shown in FIG. 13. The dust filter 119 is so shaped, bycutting a part of a disc, defining one side. The piezoelectric elements120 a and 120 b are arranged parallel to the side, are made rigid andsymmetrical, and can achieve a desirable vibrational state.

The dust filter 119 shown in FIG. 13 is not rectangular, having neitherlong sides nor short sides. Imagine a virtual rectangle 185, one side ofwhich is the side formed by cutting a part of the disc. A side oppositeto the side thus formed extends along the outer lateral edge of thepiezoelectric element 120 b. The virtual rectangle 185 has two othersides parallel and opposite to each other, so that it has the same areaas the dust filter 119. The long sides and short sides of the virtualrectangle 185 are set as the long sides and short sides of the dustfilter 119 shown in FIG. 13.

In the configuration of FIG. 13, the piezoelectric elements 120 a and120 b are not arranged symmetrically to each other with respect of thesymmetry axis of the dust filter 119. Nonetheless, the piezoelectricelements 120 a and 120 b are arranged symmetrically with respect to thesymmetry axis of the virtual rectangle 185. The same advantages cantherefore be attained as in the case where the piezoelectric elements120 a and 120 b are arranged symmetrically to each other with respect ofthe symmetry axis of the dust filter 119.

The dust filter 119 is supported as follows. The seal 150 so shaped asshown in FIG. 2B (shaped like, as it were, a deformed athletic track) isinterposed between the dust filter 119 and the holder 145. Such apushing member 151 as shown in FIG. 2A pushes the dust filter 119. Thedust filter 119 is thereby held in position. The seal 150 has the lippart 150 a. The lip part 150 a contacts the dust filter 119, sealing thespace defined by the dust filter 119, holder 145, optical LPF 118 andseal 150. Further, cushion members 156 are provided on the holder 145 atthree points. They support the dust filter 119 when an external force isexerted on the seal 150. The seal 150 contacts the dust filter 119, atits track-shaped lip part 150 a. The seal 150 therefore extends alongthe node area of vibration generated in the dust filter 119 andsurrounding the center of the dust filter 119. Hence, the seal 150 lessimpeding the vibration of the dust filter 119 than otherwise. Since thecorners (and lip part 150 a) of the seal 150 are obtuse-angled, theywill be scarcely deformed when the seal 150 receives an external force.This is why the corners of the seal 150 are not arced as in theconfiguration of FIG. 2B.

FIG. 14 shows another modification of the vibrator 159. This modifiedvibrator 159 has a dust filter 119 is formed by cutting a circular platealong two parallel lines, forming two parallel sides. That is, themodified vibrator 159 uses a dust filter 119 that has two sidessymmetric with respect to the symmetry axis extending in theY-direction. In this case, actuate piezoelectric elements 120 a and 120b are arranged not on the straight sides, but on the curved partsdefining a circle. Since the dust filter 1 is so shaped, thepiezoelectric elements 120 a and 120 b are arranged, efficientlyproviding a smaller vibrator 159. The dust filter 119 of FIG. 1 is notrectangular, either. It has two long sides, but not two short sides.Therefore, a virtual rectangle 185 is set for the dust filter 119, inthe same mariner as for the dust filter 119 of FIG. 13. That is, the twoparallel, sides of the dust filter 119, which have been defined bycutting a disc, are used as two opposite sides of the virtual rectangle185. The virtual rectangle 185 has two other sides so that it may havethe same area as the dust filter 119. The long sides of the virtualrectangle 185 are set as long sides of the dust filter 119, and theshort sides of the virtual rectangle 185 are set as short sides of thedust filter 119. The piezoelectric elements 120 a and 120 b and the flex160 are electrically connected, and the dust filter 119 is supported, inthe same mariner as explained with reference to FIG. 13.

A method of removing dust will be explained in detail, with reference toFIG. 15. FIG. 15 shows a cross section identical to that shown in FIG.5B. Assume that the piezoelectric elements 120 a and 120 b are polarizedin the direction of arrow 186 as shown in FIG. 15. If a voltage of aspecific frequency is applied to the piezoelectric elements 120 a and120 b at a certain time t₀, the vibrator 159 will be deformed asindicated by solid lines. At the mass point Y existing at given positiony in the surface of the vibrator 159, the vibration z in the Z-directionis expressed by Equation 2, as follows:z=A·sin(Y)·cos(ωt)  (2)where ω is the angular velocity of vibration, A is the amplitude ofvibration in the Z-direction, and Y=2πy/λ (λ: wavelength of bendingvibration).

The Equation 2 represents the standing-wave vibration shown in FIG. 5A.Thus, if y=s·λ/2 (here, s is an integer), then Y=sπ, and sin(Y)=0.Hence, a node 187, at which the amplitude of vibration in theZ-direction is zero irrespective of time, exists for every π/2. This isstanding-wave vibration. The state indicated by broken lines in FIG. 15takes place if t=kπ/ω (k is odd), where the vibration assumes a phaseopposite to the phase at time t₀.

Vibration z(Y₁) at point. Y₁ on the dust filter 119 is located at anantinode 188 of standing wave, bending vibration. Hence, the vibrationin the Z-direction has amplitude A, as expressed in Equation 3, asfollows:z(Y ₁)=A·cos(ωt)  (3)

If Equation 3 is differentiated with time, the vibration speed Vz(Y₁) atpoint Y₁ is expressed by Equation 4, below, because ω=2πf, where f isthe frequency of vibration:

$\begin{matrix}{{{Vz}\left( Y_{1} \right)} = {\frac{\mathbb{d}\left( {z\left( Y_{1} \right)} \right)}{\mathbb{d}t} = {{- 2}\pi\;{f \cdot A \cdot {\sin\left( {\omega\; t} \right)}}}}} & (4)\end{matrix}$

If Equation 4 is differentiated with time, vibration acceleration αz(Y₁)is expressed by Equation 5, as follows:

$\begin{matrix}{{{\alpha z}\left( Y_{1} \right)} = {\frac{\mathbb{d}\left( {{Vz}\left( Y_{1} \right)} \right)}{\mathbb{d}t} = {{- 4}\pi^{2}\;{f^{2} \cdot A \cdot {\cos\left( {\omega\; t} \right)}}}}} & (5)\end{matrix}$

Therefore, a dust 189 adhering at point Y₁ receives the acceleration ofEquation 5. The inertial force Fk the dust 189 receives at this time isgiven by Equation 6, as follows:Fk=αz(Y ₁)·M=−4π² f ² ·A·cos(ωt)·M  (6)where M is the mass of the dust 189.

As can be seen from Equation 6, the inertial force Fk increases asfrequency f is raised, in proportion to the square of f. However, theinertial force cannot be increased if amplitude A is small, no matterhow much frequency f is raised. Generally, kinetic energy of vibrationcan be produced, but in a limited value, if the piezoelectric elements120 a and 120 b that produce the kinetic energy have the same size.Therefore, if the frequency is raise in the same vibrational mode,vibrational amplitude A will change in inverse proportion to the squareof frequency f. Even if the resonance frequency is raised to achieve ahigher-order resonance mode, the vibrational frequency will fall, notincreasing the vibration speed or the vibration acceleration. Rather, ifthe frequency is raised, ideal resonance will hardly be accomplished,and the loss of vibrational energy will increase, inevitably decreasingthe vibration acceleration. That is, the mode cannot attain largeamplitude if the vibration is produced in a resonance mode that useshigh frequency only. The dust removal efficiency will be much impaired.In order to increase the vibration speed, it is therefore necessary notonly to raise the vibrational frequency, but also to generate efficientresonance at the dust filter 119 (that is, to increase the vibrationalamplitude).

Further, how large a vibrational amplitude the vibrator 159 includingthe dust filter 119 produced has achieved is detected. From thevibrational amplitude thus detected and from the vibrational frequency(i.e., frequency input from the circuit), the vibration speed andvibrational acceleration can be calculated and the dust removalefficiency can be detected. If the dust removal efficiency is detectedbefore the camera is assembled, it can be determined whether thevibrator 159 produced is a good one, and whether the vibrator 159 isappropriately pushed and supported.

Although the dust filter 119 is rectangular, the peak ridges 177 ofvibrational amplitude form closed loops around the optical axis in thevibrational mode of the embodiment, which is shown in FIG. 5A. In thevibrational mode of the embodiment, which is shown in FIG. 8, the peakridges 177 of vibrational amplitude form curves surrounding the midpointof each side. The wave reflected from the side extending in theX-direction and the wave reflected from the side extending in theY-direction are efficiently synthesized, forming a standing wave. Themethod of supporting the dust filter 119 in this vibrational mode isidentical to the method explained with reference to FIG. 5A. FIG. 8shows a seal contact area 190 and support areas 191. In the seal contactarea 190, the seal 150 contacts the dust filter 119. In the supportareas 191, the cushion members 156 support the dust filter 119 when anexternal force acts on the dust filter 119. The seal contact area 190and the support areas 191 are located near vibration nodes area 176 andare small areas in which the vibrational amplitude is small. Hence, theyscarcely impede the vibration generated in the dust filter 119.

The shape and size of the dust filter 119 greatly contribute, toefficient generation of this synthesized standing wave. As seen fromFIG. 10, it is better to set the aspect ratio (short side/long side,i.e., ratio of the length of the short sides to that of the long sidesof the dust filter 119) to a value smaller than 1, than to 1 (to makethe dust filter 119 square). If the aspect ratio is smaller than 1, thespeed of vibration at the center of the dust filter 119, in theZ-direction will be higher (the vibration speed ratio is 0.7 or more),no matter how the piezoelectric elements 120 a and 120 b are arranged.In FIG. 10, the ratio (V/V_(max)) of the vibration speed V to themaximum vibration speed V_(max) possible in this region is plotted onthe ordinate. The maximum aspect ratio (i.e., short side/long side) is,of course, 1. At the aspect ratio of 0.9 or less, the vibration speedabruptly decreases. Therefore, the dust filter 119 preferably has anaspect ratio (short side/long side) of 0.9 to 1, but less than 1. Thetwo dots in FIG. 10, which pertain to the case where the 120 a and 120 bare arranged parallel to the short sides of the dust filter 119,indicate vibration speed ratios, which are smaller than the vibrationspeed ratios attainable if the piezoelectric elements 120 a and 120 bare arranged parallel to the long sides of the dust filter 119. It istherefore advisable to arrange the piezoelectric elements 120 a and 120b at the long sides of the dust filter 119, not at the short sidesthereof. If the elements 120 a and 120 b are so arranged, the vibrationspeed ratio will increase to achieve a high dust removal ability. Themaximum vibration speed ratio is attained in FIG. 10 in the case wherethe vibrational mode is that of FIG. 5A and γ=+π/4 in the equation (1).

In vibration wherein the peak ridges 177 of vibrational amplitude formclosed loops around the optical axis or the peak ridges 177 form curvessurrounding the midpoint of each side, the dust filter 119 can undergovibration of amplitude a similar to that of concentric vibration thatmay occur if the dust filter 119 has a disc shape. In any vibrationalmode in which the amplitude is simply parallel to the side, thevibration acceleration is only 10% or more of the acceleration achievedin this embodiment.

In the vibration wherein the peak ridges 177 of vibrational amplitudeform closed loops or curves surrounding the midpoint of each side, thevibrational amplitude is the largest at the center of the vibrator 159and small at the closed loop or the curve at circumferential edges.Thus, the dust removal capability is maximal at the center of the image.If the center of the vibrator 159 is aligned with the optical axis, theshadow of dust 189 will not appear in the center part of the image,which has high image quality. This is an advantage. The vibrationalamplitude gradually decreases from the center of the dust filter 119toward the circumference thereof. The vibrational amplitude region cantherefore be easily made asymmetrical with respect to the centerline ofthe vibration application parts 178 of the piezoelectric elements 120 aand 120 b. This simple configuration can serve to detect the vibration.

In the vibration node areas 176, which exist in the focusing-beampassing area 149, the nodes 187 may be changed in position by changingthe drive frequencies of the piezoelectric elements 120 a and 120 b.Then, the elements 120 a and 120 b resonate in a different vibrationalmode, whereby the dust 189 can be removed, of course. The highvibrational acceleration generated by the vibrator 159 changes with thedeviation of the material, shape, size and position of its components(i.e., dust filter 119 and piezoelectric elements 120 a and 120 b) fromdesign specifications. In addition, the vibration speed of the vibrator159 changes with the change in the manner of holding the flex 160, withdeviation the pushing force applied to the vibrator 159 from thespecifications and with the deviation of the support members from thespecifications. In view of this, it is very important to detect thevibrational acceleration. The vibrational acceleration can be detectedeasily and accurately in the present embodiment. (What can be detectedin practice is the piezoelectric voltage generated by vibration.Nonetheless, the vibrational acceleration can be detected by detectingthe frequency because the piezoelectric voltage detected is highlycollated with the vibration speed as shown in FIG. 11.) Thus, thevibrator 139 or the vibrating device incorporating the vibrator 159 canbe evaluated as a defective one if the vibrator 159 cannot achieve aprescribed vibration speed because of the deviation of the variousparameters mentioned above. Moreover, the vibrator 159 can be madesmall, because additional vibration detecting members need not be usedas in the conventional vibrating device. Furthermore, vibrating devicethat generates vibration at a higher efficiency can be provided, becausethe vibrator 159 has no superfluous components.

A vibration state that is attained if the piezoelectric elements 120 aand 120 b are driven at a frequency near the resonance frequency will bedescribed with reference to FIGS. 16A and 16B. FIG. 16A shows anequivalent circuit that drives the piezoelectric elements 120 a and 120b at a frequency near the resonance frequency of the vibrator 159. InFIG. 16A, C₀ is the electrostatic capacitance attained as long as thepiezoelectric elements 120 a and 120 b remain connected in parallel, andL, C and R are the values of a coil, capacitor and resistor thatconstitute an electric circuit equivalent to the mechanical vibration ofthe vibrator 159. Naturally, these values change with the frequency.

When the frequency changes to resonance frequency f₀, L and C achieveresonance as is illustrated in FIG. 16B. As the frequency is graduallyraised toward the resonance frequency from the value at which noresonance takes place, the vibration phase of the vibrator 159 changeswith respect to the phase of vibration of the piezoelectric elements 120a and 120 b. When the resonance starts, the phase reaches π/2. As thefrequency is further raised, the phase reaches π. If the frequency israised even further, the phase starts decreasing. When the frequencycomes out of the resonance region, the phase becomes equal to the phasewhere no resonance undergoes at low frequencies. In the actualsituation, however, the vibration state does not become ideal. The phasedoes not change to π in some cases. Nonetheless, the drive frequency canbe set to the resonance frequency.

Support areas 191 existing at the four corners, which are shown in FIG.5A and FIG. 8, are areas in which virtually no vibration takes place.Therefore, when pushed in Z direction with an external force, theseparts hold the dust filter 119 through the cushion members 156 that aremade of vibration-attenuating material such as rubber. So held, the dustfilter 119 can be reliably supported without attenuating the vibration,because the lip part 150 a of the seal 150 displaces only a little andthe pushing force of the seal 150 does not increase. Moreover, the lippart 150 a reliably restores its initial shape it is released from theexternal force. Made of rubber or the like, the cushion members 153 canallow the dust filter 119 to vibrate in plane and never attenuate thein-plane vibration of the dust filer. The user may remove the exchangelens and may then remove fine dust particles from the surface of thedust filter 119, using a cleaning device. While being so cleaned, thedust filter 119 may receive an external force. In this case, theexternal force would act directly on the seal 150, twisting the seal150, if the supporting/pushing structure had not the configurationaccording to this embodiment. Even after released from the externalforce, the lip part 150 a of the seal 150 should remain deformed, notrestoring its initial shape. The dust filter 119 most be cleaned for thefollowing reason. That is, fine dust particles and fine liquid particlescannot be removed by vibrating the dust filter 119, as will be explainedlater. Many fine dust particles remaining on the dust filter 119 lowerthe transmittance the dust filter 119 has with respect to afocusing-beam, as will be explained later. Hence, the surface of thedust filter 119 must be cleaned if it is excessively unclean with finedust particles or fine liquid particles.

On the other hand, the seal 150 must be provided in the area havingvibrational amplitude, too. In the vibrational mode of the presentinvention, the peripheral vibrational, amplitude is small. In view ofthis, the lip part 150 a of the seal 150 holds the circumferential partof the dust filter 119 and receives a small pressing force. As a result,the force does not greatly act in the amplitude direction of bendingvibration. Therefore, the seal 156 attenuates, but very little, thevibration whose amplitude is inherently small. As shown in FIG. 5A, FIG.7B and FIG. 8, as many seal-contact parts 190 as possible contact thenode areas 176 in which the vibrational amplitude is small. This furtherreduces the attenuation of vibration. If this support configuration isemployed, the hindrance of vibration will greatly change because of thematerial of the seal 150 and the deviation of the pushing force and sizeof the seal 150 from the specifications. Further, visual inspection canhardly determine whether the seal 150 has been distortedly assembledinto the vibrating device. In the present embodiment, the voltagecollated with the vibrational amplitude (or vibration speed) pertainingto the dust filter 119 can be easily detected. Any defective product cantherefore be easily detected.

The prescribed frequency at which to vibrate the piezoelectric elements120 a and 120 b is determined by the shape, dimensions, material andsupported state of the dust filter 119, which is one component of thevibrator 159. In most cases, the temperature influences the elasticitycoefficient of the vibrator 159 and is one of the factors that changethe natural frequency of the vibrator 159. Therefore, it is desirable tomeasure the temperature of the vibrator 159 and to consider the changein the natural frequency of the vibrator 159, before the vibrator 159 isused. A temperature sensor (not shown) is therefore connected to atemperature measuring circuit (not shown), in the digital camera 10. Thevalue by which to correct the vibrational frequency of the vibrator 159in accordance with the temperature detected by the temperature sensor isstored in the nonvolatile memory 128. Then, the measured temperature andthe correction value are read into the Bucom 101. The Bucom 101calculates a drive frequency, which is used as drive frequency of thedust filter control circuit 121. Thus, vibration can be produced, whichis efficient with respect to temperature changes, as well.

The dust filter control circuit 121 of the digital camera 10 accordingto this invention will be described below, with reference to FIGS. 17and 18. The dust filter control circuit 121 has such a configuration asshown in FIG. 17. The components of the dust filter control circuit 121produce signals (Sig1 to Sig4) of such waveforms as shown in the timingchart of FIG. 18. These signals will control the dust filter 119, aswill be described below.

More specifically, as shown in FIG. 17, the dust filter control circuit121 comprises a N-scale counter 192, a half-frequency dividing circuit193, an inverter 194, a plurality of MOS transistors Q₀₀, Q₀₁ and Q₀₂, atransformer 195, and a resistor R₀₀.

The dust filter control circuit 121 is so configured that a signal(Sig4) of the prescribed frequency is produced at the secondary windingof the transformer 195 when MOS transistors Q₀₁ and Q₀₂ connected to theprimary winding of the transformer 195 are turned on and off. The signalof the prescribed frequency drives the piezoelectric elements 120 a and120 b, thereby causing the vibrator 159, to which the dust filter 119 issecured, to produce a resonance standing wave.

The Bucom 101 has two output ports P_PwCont and D_NCnt provided ascontrol ports, and a clock generator 196. The output ports P_PwCont andP_NCnt and the clock generator 196 cooperate to control the dust filtercontrol circuit 121 as follows. The clock generator 196 outputs a pulsesignal (basic clock signal) having a frequency much higher than thefrequency of the signal that will be supplied to the piezoelectricelements 120 a and 120 b. This output signal is signal Sig1 that has thewaveform shown in the timing chart of FIG. 18. The basic clock signal isinput to the N-scale counter 192.

The N-scale counter 192 counts the pulses of the pulse signal. Everytime the count reaches a prescribed value “N,” the N-scale counter 192produces a count-end pulse signal. Thus, the basic clock signal isfrequency-divided by N. The signal the N-scale counter 192 outputs issignal Sig2 that has the waveform shown in the timing chart of FIG. 18.

The pulse signal produced by means of frequency division does not have aduty ratio of 1:1. The pulse signal is supplied to the half-frequencydividing circuit 193. The half-frequency dividing circuit. 193 changesthe duty ratio of the pulse signal to 1:1. The pulse signal, thuschanged in terms of duty ratio, corresponds to signal Sig3 that has thewaveform shown in the timing chart of FIG. 18.

While the pulse signal, thus changed in duty ratio, is high, MOStransistor Q₀₁ to which this signal has been input is turned on. In themeantime, the pulse signal is supplied via the inverter 194 to MOStransistor Q₀₂. Therefore, while the pulse signal (signal Sig3) is lowstate, MOS transistor Q₀₂ to which this signal has been input is turnedon. Thus, the transistors Q₀₁ and Q₀₂, both connected to the primarywinding of the transformer 195, are alternately turned on. As a result,a signal Sig4 of such frequency as shown in FIG. 18 is produced in thesecondary winding of the transformer 195.

The winding ratio of the transformer 195 is determined by the outputvoltage of the power-supply circuit 135 and the voltage needed to drivethe piezoelectric elements 120 a and 120 b. Note that the resistor R₀₀is provided to prevent an excessive current from flowing in thetransformer 195.

In order to drive the piezoelectric elements 120 a and 120 b, MOStransistor Q₀₀ must be on, and a voltage must be applied from thepower-supply circuit 135 to the center tap of the transformer 195. Inthis case, MOS transistor Q₀₀ is turned on or off via the output portP_PwCont of the Bucom 101. Value “N” can be set to the N-scale counter192 from the output port D_NCnt of the Bucom 101. Thus, the Bucom 101can change the drive frequency for the piezoelectric elements 120 a and120 b, by appropriately controlling value “N.”

The frequency can be calculated by using Equation 7, as follows:

$\begin{matrix}{{fdrv} = \frac{fpls}{2\; N}} & (7)\end{matrix}$where N is the value set to the N-scale counter 192, fpls is thefrequency of the pulse output from the clock generator 196, and fdrv isthe frequency of the signal supplied to the piezoelectric elements 120 aand 120 b.

The calculation based on Equation 7 is performed by the CPU (controlunit) of the Bucom 101.

If the dust filter 119 is vibrated at a frequency in the ultrasonicregion (i.e., 20 kHz or more), the operating state of the dust filter119 cannot be aurally discriminated, because most people cannot hearsound falling outside the range of about 20 to 20,000 Hz. This is whythe operation display LCD 129 or the operation display LED 130 has adisplay unit for showing how the dust filter 119 is operating, to theoperator of the digital camera 10. More precisely, in the digital camera10, the vibrating members (piezoelectric elements 120 a and 120 b)imparts vibration to the dust-screening member (dust filter 119) that isarranged in front of the CCD 117, can be vibrated and can transmitlight. In the digital camera 10, the display unit is operated ininterlock with the vibrating member drive circuit (i.e., dust filtercontrol circuit 121), thus informing how the dust filter 119 isoperating (later described in detail).

To explain the above-described characteristics in detail, the controlthe Bucom 101 performs will be described with reference to FIGS. 19A to23. FIGS. 19A and 19B show the flowchart that relates to the controlprogram, which the Bucom 101 starts executing when the power switch (notshown) provided on the body unit 100 of the camera 10 is turned on.

First, a process is performed to activate the digital camera 10 (StepS101). That is, the Bucom 101 control the power-supply circuit 135. Socontrolled, the power-supply circuit 135 supplies power to the othercircuit units of the digital camera 10. Further, the Bucom 101initializes the circuit, components.

Next, the Bucom 101 calls a sub-routine “silent vibration,” vibratingthe dust filter 119, making no sound (that is, at a frequency fallingoutside the audible range) (Step S102). The “audible range” ranges fromabout 200 to 20,000 Hz, because most people can hear sound fallingwithin this range.

Steps S103 to S124, which follow, make a group of steps that iscyclically repeated. That is, the Bucom 101 first detects whether anaccessory has been attached to, or detached from, the digital camera 10(Step S103). Whether the lens unit 200 (i.e., one of accessories), forexample, has been attached to the body unit 100 is detected. Thisdetection, e.g., attaching or detaching of the lens unit 200, isperformed as the Bucom 101 communicates with the Lucom 201.

If a specific accessory is detected to have been attached to the bodyunit 100 (YES in Step S104), the Bucom 101 calls a subroutine “silentvibration” and causes the dust filter 119 to vibrate silently (StepS105).

While an accessory, particularly the lens unit 200, remains not attachedto the body unit 100 that is the camera body, dust is likely to adhereto each lens, the dust filter 119, and the like. It is thereforedesirable to perform an operation of removing dust the time when it isdetected that the lens unit 200 is attached to the body unit 100. It ishighly possible that dust adheres as the outer air circulates in thebody unit 100 at the time a lens is exchanged with another. It istherefore advisable to remove dust when a lens is exchange with another.Then, it is determined that photography will be immediately performed,and the operation goes to Step S106.

If a specific accessory is not detected to have been attached to thebody unit 100 (NO in Step S104), the Bucom 101 goes to the next step,i.e., Step S106.

In Step S106, the Bucom 101 detects the state of a specific operationswitch that the digital camera 10 has.

That is, the Bucom 101 determines whether the first release switch (notshown), which is a release switch, has been operated from the on/offstate of the switch (Step S107). The Bucom 101 reads the state. If thefirst release switch has not been turned on for a predetermined time,the Bucom 101 discriminates the state of the power switch (Step S108).If the power switch is on, the Bucom 101 returns to Step S103. If thepower switch is off, the Bucom 101 performs an end-operation (e.g.,sleep).

On the other hand, the first release switch may be found to have beenturned on in Step S107. In this case, the Bucom 101 acquires theluminance data about the object, from the photometry circuit 115, andcalculates from this data an exposure time (Tv value) and a diaphragmvalue (Av value) that are optimal for the image acquisition unit 106 andlens unit 200, respectively (Step S109).

Thereafter, the Bucom 101 acquires the detection data from the AF sensorunit 109 through the AF sensor drive circuit 110, and calculates adefocus value from the detection data (Step S110). The Bucom 101 thendetermines whether the defocus value, thus calculated, falls within apreset tolerance range (Step S111). If the defocus value does not fallwithin the tolerance range, the Bucom 101 drives the photographic lens202 (Step S112) and returns to Step S103.

On the other hand, the defocus value may falls within the tolerancerange. In this case, the Bucom 101 determines whether the second releaseswitch (not shown), which is another release switch, has been operated(Step S114). If the second release switch is on, the Bucom 101 goes toStep S115 and starts the prescribed photographic operation (laterdescribed in detail). If the second release switch is off, the Bucom 101returns to Step S108.

During the image acquisition operation, the electronic image acquisitionis controlled for a time that corresponds to the preset time forexposure (i.e., exposure time), as in ordinary photography.

As the above-mentioned photographic operation, Steps S115 to S121 areperformed in a prescribed order to photograph an object. First, theBucom 101 transmits the Av value to the Lucom 201, instructing the Lucom201 to drive the diaphragm 203 (Step S115). Thereafter, the Bucom 101moves the quick return mirror 105 to the up position (Step S116). Then,the Bucom 101 causes the front curtain of the shutter 108 to startrunning, performing open control (Step S117). Further, the Bucom 101makes the image process controller 126 perform “image acquisitionoperation” (Step S118). When the exposure to the CCD 117 (i.e.,photography) for the time corresponding to the Tv value ends, the Bucom101 causes the rear curtain of the shutter 108 to start running,achieving CLOSE control (Step S119). Then, the Bucom 101 drives thequick return mirror 105 to the down position and cocks the shutter 108(Step S120).

Then, the Bucom 101 instructs the Lucom 210 to move the diaphragm 203back to the open position (Step S121). Thus, a sequence of imageacquisition steps is terminated.

Next, the Bucom 101 determines whether the recording medium 127 isattached to the body unit 100 (Step S122). If the recording medium. 127is not attached, the Bucom 101 displays an alarm (Step S123). The Bucom101 then returns to Step S103 and repeats a similar sequence of steps.

If the recording medium 127 is attached, the Bucom 101 instructs theimage process controller 126 to record the image data acquired byphotography, in the recording medium 127 (Step S124). When the imagedata is completely recorded, the Bucom 101 returns to Step S103 againand repeats a similar sequence of steps.

In regard to the detailed relation between the vibration state and thedisplaying state will be explained in detail, the sequence ofcontrolling the “silent vibration” subroutine will be explained withreference to FIGS. 20 to 23. The term “vibration state” means the stateof the vibration induced by the piezoelectric elements 120 a and 120 b,i.e., vibrating members. FIG. 24 shows the form of a resonance-frequencywave that is continuously supplied to the vibrating members duringsilent vibration. The subroutine of FIG. 20, i.e., “silent vibration,”and the subroutine of FIGS. 21 to 23, i.e., “display process” areroutines for accomplishing vibration exclusively for removing dust fromthe dust filter 119. Vibrational frequency f₀ is set to a value close tothe resonance frequency of the dust filter 119. In the vibrational modeof FIG. 5A, for example, the vibrational frequency is 91 kHz, higherthan at least 20 kHz, and produces sound not audible to the user.

As shown in FIG. 20, when the “silent vibration.” is called, the Bucom101 first reads the data representing the drive time (Toscf0) and drivefrequency (resonance frequency: Noscf0) from the data stored in aspecific area of the nonvolatile memory 128 (Step S201). At this timing,the Bucom 101 causes the display unit provided in the operation displayLCD 129 or operation display LED 130 to turn on the vibrational modedisplay, as shown in FIG. 21 (Step S301). The Bucom 101 then determineswhether a predetermined time has passed (Step S302). If thepredetermined time has not passed, the Bucom 101 makes the display unitkeep turning on the vibrational mode display. Upon lapse of thepredetermined time, the Bucom 101 turns off the displaying of thevibrational mode display (Step S303).

Next, the Bucom 101 outputs the drive frequency Noscf0 from the outputport D_NCnt to the N-scale counter 192 of the dust filter controlcircuit 121 (Step S202).

In the following steps S203 to S205, the dust is removed as will bedescribed below. First, the Bucom 101 sets the output port P_PwCont toNigh, thereby starting the dust removal (Step S203). At this timing, theBucom 101 starts displaying the vibrating operation as shown in FIG. 22(Step S311). The Bucom 101 then determines whether or riot thepredetermined time has passed (Step S312). If the predetermined time hasnot passed, the Bucom 101 keeps displaying the vibrating operation. Uponlapse of the predetermined time, the Bucom 101 stops displaying of thevibrating operation (Step S313). The display of the vibrating operation,at this time, changes as the time passes or as the dust is removed (howit changes is not shown, though). The predetermined time is almost equalto Toscf0, i.e., the time for which the vibration (later described)continues.

If the output port P_PwCont is set to High in Step S203, thepiezoelectric elements 120 a and 120 b vibrate the dust filter 119 atthe prescribed vibrational frequency (Noscf0), removing the dust 189from the surface of the dust filter 119. At the same time the dust isremoved from the surface of the dust filter 119, air is vibrated,producing an ultrasonic wave. The vibration at the drive frequencyNoscf0, however, does not make sound audible to most people. Hence, theuser hears nothing. The Bucom 101 waits for the predetermined timeToscf0, while the dust filter 119 remains vibrated (Step S204). Uponlapse of the predetermined time Toscf0, the Bucom 101 sets the outputport P_PwCont to Low, stopping the dust removal operation (Step S205).At this timing, the Bucom 101 turns on the display unit, whereby thedisplaying of the vibration-end display is turned on (Step S321). Whenthe Bucom 101 determines (in Step S322) that the predetermined time haspassed, the displaying of the vibration-end display is turned off (StepS323). The Bucom 101 then returns to the step next to the step in whichthe “silent vibration” is called.

The vibrational frequency f₀ (i.e., resonance frequency Noscf0) and thedrive time (Toscf0) used in this subroutine define such a waveform asshown in the graph of FIG. 24. As can be seen from this waveform,constant vibration (f₀=91 kHz) continues for a time (i.e., Toscf0) thatis long enough to accomplish the dust removal.

That is, the vibrational mode adjusts the resonance frequency applied tothe vibration application unit 178, controlling the dust removal.

In the first embodiment described above, whether normal vibration hasbeen generated can easily and reliably determined even if thedust-screening member is miniaturized. This can provide a smallvibrating device having high dust removal ability, which can beincorporated in various products without the necessity of adding specialcomponents after the inspection.

Further, the dust-screening member can undergo standing-wave vibrationthat can increase the vibrational amplitude to a maximum.

Still further, an intensity of a voltage signal of high levelcorresponding to the amplitude of the standing-wave vibration can bereliably acquired, because the vibrating member assumes symmetricalweight balance and also because the second vibration application partreceiving vibration is asymmetrical with respect to the nodes ofstanding-wave vibration.

Second Embodiment

The subroutine “silent vibration” called in the camera sequence (mainroutine) that the Bucom performs in a digital camera that is a secondembodiment of the image equipment according to this invention will bedescribed with reference to FIG. 25. FIG. 25 illustrates a modificationof the subroutine “silent vibration” shown an FIG. 20. The secondembodiment differs from the first embodiment in the operating mode ofthe dust filter 119. In the first embodiment, the dust filter 119 isdriven at a fixed frequency, i.e., frequency f₀, producing a standingwave. By contrast, in the second embodiment, the drive frequency isgradually changed, thereby achieving large-amplitude vibration atvarious frequencies including the resonance frequency, without strictlycontrolling the drive frequency.

If the aspect ratio shown in FIG. 10 has changed from the design valueof 0.9, during the manufacture, the vibrational mode will greatly change(that is, the vibration speed ratio will abruptly change). Therefore, aprecise resonance frequency must be set in each product and thepiezoelectric elements 120 a and 120 b must be driven at the frequencyso set. This is because the vibration speed will further decrease if thepiezoelectric elements are driven at any frequency other than theresonance frequency. An extremely simple circuit configuration can,nonetheless, drive the piezoelectric elements precisely at the resonancefrequency if the frequency is controlled as in the second embodiment. Amethod of control can therefore be achieved to eliminate any differencein resonance frequency between the products.

In the subroutine “silent vibration” of FIG. 25, the vibrationalfrequency f₀ is set to a value close to the resonance frequency of thedust filter 119. The vibrational frequency f₀ is 91 kHz in, for example,the vibrational mode of FIG. 5A. That is, the vibrational frequencyexceeds at least 20 kHz, and makes sound not audible to the user.

First, the Bucom 101 reads the data representing the drive time(Toscf0), drive-start frequency (Noscfs), frequency change value (Δf)and drive-end frequency (Noscft), from the data stored in a specificarea of the nonvolatile memory 128 (Step S211). At this timing, theBucom 101 causes the display unit to display the vibrational mode asshown in FIG. 21, in the same way as in the first embodiment.

Next, the Bucom 101 sets the drive-start frequency (Noscfs) as drivefrequency (Noscf) (Step S212). The Bucom 101 then outputs the drivefrequency (Noscf) from the output port D_NCnt to the N-scale counter 192of the dust filter control circuit 121 (Step S213).

In the following steps S203 et seq., the dust is removed as will bedescribed below. First, the dust removal is started. At this time, thedisplay of the vibrating operation is performed as shown in FIG. 22, asin the first embodiment.

First, the Bucom 101 sets the output port P_PwCont to High, to achievedust removal (Step S214). The piezoelectric elements 120 a and 120 bvibrate the dust filter 119 at the prescribed vibrational frequency(Noscf), producing a standing wave of a small amplitude at the dustfilter 119. The dust 189 cannot be removed from the surface of the dustfilter 119, because the vibrational amplitude is small. This vibrationcontinues for the drive time (Toscf0) (Step S215). Upon lapse of thisdrive time (Toscf0), the Bucom 101 determines whether the drivefrequency (Noscf) is equal to the drive-end frequency (Noscft) (Step216). If the drive frequency is not equal to the drive-end frequency (NOin Step S216), the Bucom 101 adds the frequency change value (Δf) to thedrive frequency (Noscf), and sets the sum to the drive frequency (Noscf)(Step S211). Then, the Bucom 101 repeats the sequence of Steps S212 toS216.

If the drive frequency (Noscf) is equal to the drive-end frequency(Noscft) (YES in Step S216), the Bucom 101 sets the output port P_PwContto Low, stopping the vibration of the piezoelectric elements 120 a and120 b (Step S218), thereby terminating the “silent vibration.” At thispoint, the display of vibration-end is performed as shown in FIG. 23, asin the first embodiment.

As the frequency is gradually changed as described above, the amplitudeor the standing wave increases. In view of this, the drive-startfrequency (Ncoscfs), the frequency change value (Δf) and the drive-endfrequency (Noscft) are set so that the resonance frequency of thestanding wave may be surpassed. As a result, a standing wave of smallvibrational amplitude is produced at the dust filter 119. The standingwave can thereby controlled, such that its vibrational amplitudegradually increases until it becomes resonance vibration, and thendecreases thereafter. If the vibrational amplitude (corresponding tovibration speed) is larger than a prescribed value, the dust 189 can beremoved. In other words, the dust 189 can be removed while thevibrational frequency remains in a prescribed range. This range is broadin the present embodiment, because the vibrational amplitude is largeduring the resonance.

If the difference between the drive-start frequency (Noscfs) and thedrive-end frequency (Noscft) is large, the fluctuation of the resonancefrequency, due to the temperature of the vibrator 159 or to thedeviation in characteristic change of the vibrator 159, during themanufacture, can be absorbed. Hence, the dust 189 can be reliablyremoved from the dust filter 119, by using an extremely simple circuitconfiguration.

Further, this circuit configuration should better be applied to the dustfilter drive circuit 184A of the vibration detector 184 shown in FIG.12. If the dust filter drive circuit 184A has this configuration, thefrequency at which the vibration detection voltage is maximal becomesresonance frequency even if the resonance frequency of vibrational modechanges because the components of the vibrator 159 deviate from thespecifications, in terms of the materials, sizes and assembling manner.The resonance frequency and the voltage at the resonance frequency cantherefore be detected easily.

The second embodiment so configured can achieve almost the sameadvantages as the first embodiment described above. Moreover, the secondembodiment can generate vibration of a large amplitude, without thenecessity of strictly controlling the drive frequency, thereby reliablyremoving the dust. Further, even if the drive frequency changes as theambient temperature changes, the control method need not be altered.

Third Embodiment

FIG. 26 is a diagram showing the configuration of the vibration detectorused in a third embodiment of this invention. More precisely, FIG. 26shows the circuit configuration of the vibration detector 184. Thecomponents identical to those of the first and second embodiments aredesignated by the same reference numbers and will, not be described.Only the characterizing features of the second embodiments will bedescribed.

The circuit configuration of FIG. 26 pertains to a camera thatincorporates a vibration detector 184. The configuration of FIG. 26differs from that of FIG. 12 in that a switch 197 is used as aconnection unit in place of the connection terminals 160 j and 160 k ofthe flex 160. The switch 197 may be a mechanical switch or an electricalswitch such as a transistor. The switch 197 can connect and disconnectthe first circuit and the second circuit more easily and reliably thanin the first and second embodiments, in which the first and secondcircuits are connected by soldering and not connected by performing nosoldering.

The configuration of FIG. 26 can easily switch two states, from one tothe other, whereby the dust filter control circuit 121 drives bothpiezoelectric elements 120 a and 120, or the voltage detection circuit184B detects the voltage across one piezoelectric element, while thedust filter control circuit 121 is driving the other piezoelectricelement. Hence, the circuit according to the first embodiment can setthe frequency for the camera, if the resonance frequency is inferredfrom the vibration voltage detected by the voltage detection circuit184B and if the resonance frequency thus inferred is utilized.Furthermore, from the voltage level detected, it can be determinedwhether the vibration is appropriate or whether the vibrating devicenormally operates or not.

The third embodiment can achieve almost the same advantages as the firstand second embodiments described above, and can further inspect, thevibrator 159 easily and reliably even after the vibrating device hasbeen incorporated into the camera.

The present invention has been explained, describing some embodiments.Nonetheless, this invention is not limited to the embodiments describedabove. Various changes and modifications can, of course, be made withinthe scope and spirit of the invention.

For example, a mechanism that applies an air flow or a mechanism thathas a wipe may be used in combination with the dust removal mechanismhaving the vibrating member, in order to remove the dust 189 from thedust filter 119.

In the embodiments described above, the vibrating members arepiezoelectric elements. The piezoelectric elements may be replaced byelectrostrictive members or super magnetostrictive elements.

In order to remove dust more efficiently from the member vibrated, themember may be coated with an indium-tin oxide (ITO) film, which is atransparent conductive film, indium-zinc film, poly 3,4-ethylenedioxythiophene film, surfactant agent film that is a hygroscopicanti-electrostatic film, siloxane-based film, or the like. In this case,the frequency, the drive time, etc., all related to the vibration, areset to values that accord with the material of the film.

Moreover, the optical LPF 118, described as one embodiment of theinvention, may be replaced by a plurality of optical LPFs that exhibitbirefringence. Of these optical LPFs, the optical LPF located closest tothe object of photography may be used as a dust-screening member (i.e.,a subject to be vibrated), in place of the dust filter 119 shown in FIG.2A.

Further, a camera may does not have the optical LPF 118 of FIG. 2Adescribed as one embodiment of the invention, and the dust filter 119may be used as an optical element such as an optical LPF, aninfrared-beam filter, a deflection filter, or a half mirror.

Furthermore, the camera may not have the optical LPF 118, and the dustfilter 119 may be replaced by the protection glass plate 142 shown inFIG. 2A. In this case, the protection glass plate 142 and the CCD chip136 remain free of dust and moisture, and the structure of FIG. 2A thatsupports and vet vibrates the dust filter 119 may be used to support andvibrate the protection glass plate 142. Needless to say, the protectionglass plate 142 may be used as an optical element such as an opticalLPF, an infrared-beam filter, a deflection filter, or a half mirror.

The image equipment according to this invention is riot limited to theimage acquisition apparatus (digital camera) exemplified above. Thisinvention can be applied to any other apparatus that needs a dustremoval function. The invention can be practiced in the form of variousmodifications, if necessary. More specifically, a dust moving mechanismaccording to this invention may be arranged between the display elementand the light source or image projecting lens in an image projector.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A vibrating device comprising: a dust-screeningmember shaped like a plate as a whole, having front and back surfacesand having a light-transmitting region for transmitting light betweenthe front surface and the back surface; a support member configured tosupport the dust screening member, thereby to render the back surface ofthe dust-screening member airtight; a first vibrating member shapedalmost like a rectangle, arranged at a first outer circumferential partof the dust-screening member and composed of a first vibrationapplication part configured to expand and contract when supplied with anelectrical signal for expanding and contracting and a firstnon-vibration application part configured not to supplied with theelectrical signal for expanding and contracting; a second vibratingmember shaped almost like a rectangle, arranged at a second outercircumferential part of the dust-screening member, which opposes thefirst outer circumferential part of the dust-screening member, andcomposed of a second vibration application part configured to expand andcontract when supplied with the electrical signal for expanding andcontracting and a second non-vibration application part configured notto supplied with the electrical signal for expanding and contracting; aconnect member composed of a first circuit, second circuit and aconnection part, the first circuit configured to input an electricalsignal to the first vibration application part, the second circuitconfigured to output, from the second vibration application part, anelectrical signal generated in the second vibration application partbased on a vibration of the first vibration application part when anelectrical signal is input to the first circuit, and the connection partconfigured to connect the first and second circuits electrically; and adrive unit configured to drive the first and second vibrating memberswhile the first and second circuits remain connected by the connectionpart, wherein the first and second vibrating members are shapedsymmetrically to one another in weight balance with respect to a virtualsymmetry axis at the same distance from the first and second vibratingmembers and also to an virtual centerline connecting gravity centers ofthe first and second vibrating members, and the second vibrating memberwhich receives the vibration has a vibrational axis and is shapedasymmetrically in vibrational amplitude with respect to the vibrationalaxis.
 2. The device according to claim 1, wherein when driven by thedrive unit, the first and second vibrating members generate, at thedust-screening member, vibration symmetrical to a plane containing thevirtual centerline and being perpendicular to the virtual symmetry axis.3. The device according to claim 2, wherein the vibration symmetrical tothe plane is vibration forming a plurality of peak ridges that define aclosed curve around a point at which the virtual symmetry axisintersects with the virtual centerline.
 4. The device according to claim1, wherein the second vibration application part has a vibrational axiswhich is perpendicular to the virtual symmetry axis and which bisects asurface area of trio second vibration application part into equalhalves.
 5. The device according to claim 1, wherein the dust-screeningmember has an aspect ratio of equal to or greater than 0.9, but lessthan 1, the aspect ratio being a ratio of either short side to eitherlong side of a virtual rectangle that has the same area as that of thefront or back surface of the dust-screening member.
 6. An imageequipment comprising: an image forming element having an image surfaceon which an optical image is formed; a dust-screening member shaped likea plate as a whole, having front and back surfaces and having alight-transmitting region for transmitting light between the frontsurface and the back surface; a support member configured to support thedust-screening member, to space the light-transmitting region of thedust-screening member, apart from the image surface of the image formingelement by a predetermined distance, and to render the back surface ofthe dust-screening member airtight; a first vibrating member shapedalmost like a rectangle, arranged at a first outer circumferential partof the dust-screening member and composed of a first vibrationapplication part configured to expand and contract when supplied with anelectrical signal for expanding and contracting and a firstnon-vibration application part configured not to supplied with theelectrical signal for expanding and contracting; a second vibratingmember shaped almost like a rectangle, arranged at a second outercircumferential part of the dust-screening member, which opposes thefirst outer circumferential part of the dust-screening member, andcomposed of a second vibration application part configured to expand andcontract when supplied with the electrical signal for expanding andcontracting and a second non-vibration application part configured notto supplied with the electrical signal for expanding and contracting; aconnection member composed of a first circuit, second circuit and aconnection part, the first circuit configured to input an electricalsignal to the first vibration application part, the second circuitconfigured to output, from the second vibration application part, anelectrical signal generated in the second vibration application partbased on a vibration of the first vibration application part when anelectrical signal is input to the first circuit, and the connection partconfigured to connect the first and second circuits electrically; and adrive unit configured to drive the first and second vibrating memberswhile the first and second circuits remain connected by the connectionpart, wherein the first and second vibrating members are shapedsymmetrically to one another in weight balance with respect to a virtualsymmetry axis at the same distance from the first and second vibratingmembers and also to an virtual centerline connecting gravity centers ofthe first and second vibrating members, and the second vibrating memberwhich receives the vibration has a vibrational axis and is shapedasymmetrically in vibrational amplitude with respect to the vibrationalaxis.